$FSLY
Fastly Inc Stock $fsly

$fsly Overview Financials Valuation SEC Filings Company Website

2021 Q2 Form 10-Q Financial Statement

#000151741321000154 Filed on August 06, 2021

Income Statement

Concept	2021 Q2	2020 Q2	2020 Q1
Revenue	$85.03M	$74.66M	$62.92M
YoY Change	13.88%	61.7%	38.12%
Cost Of Revenue	$40.32M	$29.70M	$27.27M
YoY Change	35.77%	42.88%	38.27%
Gross Profit	$44.71M	$44.97M	$35.66M
YoY Change	-0.58%	77.11%	38.01%
Gross Profit Margin	52.58%	60.23%	56.67%
Selling, General & Admin	$71.83M	$42.75M	$33.34M
YoY Change	68.02%	65.53%	40.43%
% of Gross Profit	160.67%	95.07%	93.49%
Research & Development	$30.35M	$16.66M	$14.30M
YoY Change	82.2%	48.12%	40.51%
% of Gross Profit	67.88%	37.04%	40.1%
Depreciation & Amortization	$6.900M	$4.700M	$4.715M
YoY Change	46.81%	20.51%	26.14%
% of Gross Profit	15.43%	10.45%	13.22%
Operating Expenses	$102.2M	$59.40M	$47.64M
YoY Change	72.0%	60.25%	40.45%
Operating Profit	-$57.47M	-$14.44M	-$11.98M
YoY Change	298.03%	23.6%	48.27%
Interest Expense	$1.436M	$371.0K	$316.0K
YoY Change	287.06%	-87.59%	-74.41%
% of Operating Profit
Other Income/Expense, Net	$178.0K	-$53.00K	$402.0K
YoY Change	-435.85%	-96.88%	-151.8%
Pretax Income	-$58.45M	-$14.48M	-$11.17M
YoY Change	303.55%	-6.58%	15.5%
Income Tax	-$200.0K	$0.00	$800.0K
% Of Pretax Income
Net Earnings	-$58.30M	-$14.46M	-$11.99M
YoY Change	303.15%	-7.23%	23.27%
Net Earnings / Revenue	-68.56%	-19.37%	-19.05%
Basic Earnings Per Share	-$0.51	-$0.14
Diluted Earnings Per Share	-$0.51	-$0.14	-$125.7K
COMMON SHARES
Basic Shares Outstanding	115.3M shares	99.84M shares
Diluted Shares Outstanding	115.3M shares	99.84M shares

Balance Sheet

Concept	2021 Q2	2020 Q2	2020 Q1
SHORT-TERM ASSETS
Cash & Short-Term Investments	$929.7M	$384.0M	$116.6M
YoY Change	142.1%	56.35%	73.75%
Cash & Equivalents	$688.0M	$257.4M	$22.50M
Short-Term Investments	$241.7M	$126.6M	$94.08M
Other Short-Term Assets	$22.31M	$83.10M	$82.20M
YoY Change	-73.15%	581.15%	633.93%
Inventory
Prepaid Expenses
Receivables	$56.07M	$58.33M	$43.02M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$1.008B	$525.4M	$241.8M
YoY Change	91.87%	83.49%	126.01%
LONG-TERM ASSETS
Property, Plant & Equipment	$116.5M	$65.84M	$69.07M
YoY Change	76.91%	18.39%	45.72%
Goodwill	$635.6M	$347.0K	$348.0K
YoY Change	183083.29%	-3.34%
Intangibles	$113.2M	$2.864M	$1.089M
YoY Change	3853.04%	139.07%
Long-Term Investments	$173.2M
YoY Change
Other Assets	$27.58M	$13.40M	$11.51M
YoY Change	105.81%	4.23%	37.05%
Total Long-Term Assets	$1.129B	$82.45M	$82.02M
YoY Change	1269.08%	17.74%	44.65%
TOTAL ASSETS
Total Short-Term Assets	$1.008B	$525.4M	$241.8M
Total Long-Term Assets	$1.129B	$82.45M	$82.02M
Total Assets	$2.137B	$607.9M	$323.8M
YoY Change	251.54%	70.57%	97.83%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$10.20M	$6.087M	$9.457M
YoY Change	67.6%	5.81%	142.49%
Accrued Expenses	$28.61M	$22.63M	$20.22M
YoY Change	26.42%	-9.84%	88.95%
Deferred Revenue	$22.67M	$48.00K	$852.0K
YoY Change	47122.92%
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due	$14.77M	$5.188M	$5.291M
YoY Change	184.75%	-84.19%	-58.66%
Total Short-Term Liabilities	$103.0M	$38.31M	$40.40M
YoY Change	168.96%	-41.3%	23.54%
LONG-TERM LIABILITIES
Long-Term Debt	$931.4M	$24.86M	$26.04M
YoY Change	3646.82%	39.04%	-33.9%
Other Long-Term Liabilities	$6.502M	$2.533M	$1.357M
YoY Change	156.69%	-57.15%	-75.77%
Total Long-Term Liabilities	$937.9M	$27.39M	$27.40M
YoY Change	3324.07%	15.14%	-39.11%
TOTAL LIABILITIES
Total Short-Term Liabilities	$103.0M	$38.31M	$40.40M
Total Long-Term Liabilities	$937.9M	$27.39M	$27.40M
Total Liabilities	$1.108B	$65.70M	$67.80M
YoY Change	1586.15%	-26.23%	-12.75%
SHAREHOLDERS EQUITY
Retained Earnings	-$397.2M	-$218.5M	-$204.0M
YoY Change	81.81%	31.78%
Common Stock	$2.000K	$2.000K	$2.000K
YoY Change	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$1.029B	$541.9M	$255.8M
YoY Change
Total Liabilities & Shareholders Equity	$2.137B	$607.9M	$323.8M
YoY Change	251.54%	70.57%	97.83%

Cashflow Statement

Concept	2021 Q2	2020 Q2	2020 Q1
OPERATING ACTIVITIES
Net Income	-$58.30M	-$14.46M	-$11.99M
YoY Change	303.15%	-7.23%	23.27%
Depreciation, Depletion And Amortization	$6.900M	$4.700M	$4.715M
YoY Change	46.81%	20.51%	26.14%
Cash From Operating Activities	-$17.01M	-$8.780M	-$7.186M
YoY Change	93.77%	57.63%	-28.73%
INVESTING ACTIVITIES
Capital Expenditures	-$6.716M	-$4.930M	$10.17M
YoY Change	36.23%	-3.14%	152.65%
Acquisitions
YoY Change
Other Investing Activities	-$237.8M	-$32.69M	$21.40M
YoY Change	627.4%	-337.23%	1698.32%
Cash From Investing Activities	-$244.5M	-$37.62M	$9.794M
YoY Change	549.93%	-532.41%	-372.51%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	754.0K	281.4M	$3.714M
YoY Change	-99.73%	48.86%	-293.14%
NET CHANGE
Cash From Operating Activities	-17.01M	-8.780M	-$7.186M
Cash From Investing Activities	-244.5M	-37.62M	$9.794M
Cash From Financing Activities	754.0K	281.4M	$3.714M
Net Change In Cash	-260.8M	235.0M	$6.359M
YoY Change	-210.95%	22.29%	-140.74%
FREE CASH FLOW
Cash From Operating Activities	-$17.01M	-$8.780M	-$7.186M
Capital Expenditures	-$6.716M	-$4.930M	$10.17M
Free Cash Flow	-$10.30M	-$3.850M	-$17.36M
YoY Change	167.45%	702.08%	23.02%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Entity Central Index Key EntityCentralIndexKey	0001517413
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q2
	dei	Amendment Flag AmendmentFlag	false
	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2021-06-30
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	001-38897
	dei	Entity Registrant Name EntityRegistrantName	FASTLY, INC.
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	27-5411834
	dei	Entity Address Address Line1 EntityAddressAddressLine1	475 Brannan Street, Suite 300
	dei	Entity Address City Or Town EntityAddressCityOrTown	San Francisco
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	94107
	dei	City Area Code CityAreaCode	844
	dei	Local Phone Number LocalPhoneNumber	432-7859
	dei	Entity Address State Or Province EntityAddressStateOrProvince	CA
	dei	Security12b Title Security12bTitle	Class A Common Stock, $0.00002 par value
	dei	Trading Symbol TradingSymbol	FSLY
	dei	Security Exchange Name SecurityExchangeName	NYSE
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
CY2021Q3	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	116600000	shares
CY2021Q2	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	687986000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	62900000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	241744000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	131283000	USD
CY2021Q2	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	2947000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	3248000	USD
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CY2020Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	50258000	USD
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CY2020Q4	us-gaap	Goodwill Goodwill	635590000	USD
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CY2021Q2	us-gaap	Liabilities Current LiabilitiesCurrent	103032000	USD
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CY2021Q2	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	931385000	USD
CY2020Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	0	USD
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CY2021Q2	us-gaap	Liabilities Liabilities	1107781000	USD
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CY2021Q2	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
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CY2020Q4	us-gaap	Common Stock Value CommonStockValue	2000	USD
CY2021Q2	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	1426520000	USD
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CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	6000	USD
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CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	-288193000	USD
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	1029090000	USD
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CY2021Q2	us-gaap	Cost Of Revenue CostOfRevenue	40320000	USD
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	us-gaap	Cost Of Revenue CostOfRevenue	77814000	USD
	us-gaap	Cost Of Revenue CostOfRevenue	56962000	USD
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	us-gaap	Gross Profit GrossProfit	92064000	USD
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	us-gaap	Operating Income Loss OperatingIncomeLoss	-107431000	USD
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CY2020Q2	us-gaap	Investment Income Interest InvestmentIncomeInterest	378000	USD
	us-gaap	Investment Income Interest InvestmentIncomeInterest	450000	USD
	us-gaap	Investment Income Interest InvestmentIncomeInterest	1097000	USD
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CY2020Q2	us-gaap	Interest Expense InterestExpense	371000	USD
	us-gaap	Interest Expense InterestExpense	2097000	USD
	us-gaap	Interest Expense InterestExpense	687000	USD
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	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	795000	USD
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	us-gaap	Net Income Loss NetIncomeLoss	-108978000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-26450000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-26450000	USD
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CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	-58295000	USD
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CY2020Q2	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	-208000	USD
	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	-225000	USD
	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	270000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-124000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-302000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-267000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	189000	USD
CY2021Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-58419000	USD
CY2020Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-14762000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-109245000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-26261000	USD
CY2021Q1	us-gaap	Stockholders Equity StockholdersEquity	1045034000	USD
CY2021Q2	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	2886000	USD
CY2021Q2	fsly	Stock Issued During Period Value Vesting Of Early Exercised Stock Options StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions	64000	USD
CY2021Q2	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	5719000	USD
CY2021Q2	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	33806000	USD
CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	-58295000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-124000	USD
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	1029090000	USD
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	255798000	USD
CY2020Q2	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	274177000	USD
CY2020Q2	fsly	Stock Issued During Period Value Vesting Of Early Exercised Stock Options StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions	128000	USD
CY2020Q2	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	4247000	USD
CY2020Q2	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	5657000	USD
CY2020Q2	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	16668000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	-14460000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-302000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	541913000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	1061865000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	5605000	USD
	fsly	Stock Issued During Period Value Vesting Of Early Exercised Stock Options StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions	128000	USD
	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	5719000	USD
	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	65018000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-108978000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-267000	USD
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	1029090000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	257652000	USD
	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	274177000	USD
	fsly	Stock Issued During Period Value Vesting Of Early Exercised Stock Options StockIssuedDuringPeriodValueVestingOfEarlyExercisedStockOptions	274000	USD
	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	4247000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	8831000	USD
	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	23245000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-26450000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	189000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	541913000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-108978000	USD
	us-gaap	Net Income Loss NetIncomeLoss	-26450000	USD
	us-gaap	Depreciation Nonproduction DepreciationNonproduction	13346000	USD
	us-gaap	Depreciation Nonproduction DepreciationNonproduction	9372000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	10620000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	72000	USD
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	fsly	Amortization Of Right Of Use Assets And Other AmortizationOfRightOfUseAssetsAndOther	10188000	USD
	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	1269000	USD
	us-gaap	Amortization Of Financing Costs And Discounts AmortizationOfFinancingCostsAndDiscounts	38000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	2946000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1481000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	64264000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	22610000	USD
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	-195000	USD
	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	1016000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	735000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	268000	USD
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	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	0	USD
	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-813000	USD
	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	304000	USD
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	5612000	USD
	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	22211000	USD
	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	5494000	USD
	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	1983000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	5089000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	4769000	USD
	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	162000	USD
	us-gaap	Increase Decrease In Accounts Payable IncreaseDecreaseInAccountsPayable	1364000	USD
	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	-3835000	USD
	us-gaap	Increase Decrease In Accrued Liabilities IncreaseDecreaseInAccruedLiabilities	2626000	USD
	fsly	Increase Decrease In Operating Lease Liabilities IncreaseDecreaseInOperatingLeaseLiabilities	-12856000	USD
	fsly	Increase Decrease In Operating Lease Liabilities IncreaseDecreaseInOperatingLeaseLiabilities	-8413000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	8804000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-336000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-27883000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-15967000	USD
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	333868000	USD
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	56187000	USD
	us-gaap	Proceeds From Sale And Maturity Of Available For Sale Securities ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities	12497000	USD
	us-gaap	Proceeds From Sale And Maturity Of Available For Sale Securities ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities	0	USD
	us-gaap	Proceeds From Sale And Maturity Of Marketable Securities ProceedsFromSaleAndMaturityOfMarketableSecurities	57253000	USD
	us-gaap	Proceeds From Sale And Maturity Of Marketable Securities ProceedsFromSaleAndMaturityOfMarketableSecurities	44901000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	11013000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	12241000	USD
	us-gaap	Payments For Software PaymentsForSoftware	2680000	USD
	us-gaap	Payments For Software PaymentsForSoftware	2181000	USD
	us-gaap	Payments To Acquire Intangible Assets PaymentsToAcquireIntangibleAssets	2093000	USD
CY2021Q2	us-gaap	Payments To Acquire Intangible Assets PaymentsToAcquireIntangibleAssets	2093000	USD
	us-gaap	Payments To Acquire Intangible Assets PaymentsToAcquireIntangibleAssets	1811000	USD
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	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-27519000	USD
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	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	274896000	USD
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	us-gaap	Payments Of Stock Issuance Costs PaymentsOfStockIssuanceCosts	173000	USD
	us-gaap	Proceeds From Convertible Debt ProceedsFromConvertibleDebt	930775000	USD
	us-gaap	Proceeds From Convertible Debt ProceedsFromConvertibleDebt	0	USD
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	1351000	USD
	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	0	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	6579000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	2900000	USD
	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	4564000	USD
	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	4164000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	5605000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	8831000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	933014000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	284818000	USD
	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-141000	USD
	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-56000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	625086000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	241276000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	63880000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	86229000	USD
CY2021Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	688966000	USD
CY2020Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	327505000	USD
	us-gaap	Interest Paid Net InterestPaidNet	759000	USD
	us-gaap	Interest Paid Net InterestPaidNet	348000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	175000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	910000	USD
	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	1814000	USD
	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	3885000	USD
	fsly	Vestingof Early Exercised Stock Options VestingofEarlyExercisedStockOptions	128000	USD
	fsly	Vestingof Early Exercised Stock Options VestingofEarlyExercisedStockOptions	274000	USD
	fsly	Cashless Exercise Of Common Stock Warrants CashlessExerciseOfCommonStockWarrants	0	USD
	fsly	Cashless Exercise Of Common Stock Warrants CashlessExerciseOfCommonStockWarrants	1557000	USD
	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	754000	USD
	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	635000	USD
	fsly	Public Offering Costs Incurred But Not Yet Paid PublicOfferingCostsIncurredButNotYetPaid	0	USD
	fsly	Public Offering Costs Incurred But Not Yet Paid PublicOfferingCostsIncurredButNotYetPaid	546000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	13481000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	10278000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	15538000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	7842000	USD
CY2021Q2	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	687986000	USD
CY2020Q2	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	257418000	USD
CY2021Q2	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	87000	USD
CY2020Q2	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	70087000	USD
CY2021Q2	us-gaap	Restricted Cash And Cash Equivalents Noncurrent RestrictedCashAndCashEquivalentsNoncurrent	893000	USD
CY2020Q2	us-gaap	Restricted Cash And Cash Equivalents Noncurrent RestrictedCashAndCashEquivalentsNoncurrent	0	USD
CY2021Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	688966000	USD
CY2020Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	327505000	USD
	us-gaap	Nature Of Operations NatureOfOperations	Nature of Business<div style="margin-bottom:12pt;text-indent:27pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Fastly, Inc. has built an edge cloud platform that can process, serve, and secure its customer’s applications as close to their end users as possible. As of June 30, 2021, our edge network spans across 61 markets around the world. We were incorporated in Delaware in 2011 and are headquartered in San Francisco, California.</span></div><div style="margin-bottom:12pt;text-indent:27pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">As used herein, "Fastly," "we," "our," "the Company," and similar terms include Fastly, Inc. and its subsidiaries, unless the context indicates otherwise,</span></div><div style="margin-bottom:12pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Follow-on Public Offering </span></div><div style="margin-bottom:12pt;text-indent:36pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On May 26, 2020, we completed a follow-on public offering in which we sold 6,900,000 shares of Class A common stock, which included 900,000 shares sold pursuant to the exercise by the underwriters of an option to purchase additional shares, at the public offering price of $41.50 per share. We received net proceeds of $274.9 million, after deducting underwriting discounts and commissions, from sales of our shares in the public offering.</span></div>
CY2021Q2	fsly	Operating Markets OperatingMarkets	61	operatingMarket
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	255798000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	541913000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	257652000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	541913000	USD
	fsly	Amortization Of Deferred Rent AmortizationOfDeferredRent	0	USD
	fsly	Amortization Of Right Of Use Assets And Other AmortizationOfRightOfUseAssetsAndOther	10188000	USD
	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	304000	USD
	fsly	Increase Decrease In Operating Lease Liabilities IncreaseDecreaseInOperatingLeaseLiabilities	-8413000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-15967000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	12241000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-27519000	USD
	us-gaap	Repayments Of Long Term Capital Lease Obligations RepaymentsOfLongTermCapitalLeaseObligations	0	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	2900000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	284818000	USD
	us-gaap	Capital Lease Obligations Incurred CapitalLeaseObligationsIncurred	0	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	10278000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	7842000	USD
	us-gaap	Use Of Estimates UseOfEstimates	<div style="margin-bottom:12pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Use of Estimates</span></div><div style="margin-bottom:12pt;text-indent:27pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The preparation of our condensed consolidated financial statements requires us to make estimates, judgments, and assumptions that affect the reported amounts of assets, liabilities, revenue, costs and expenses, and related disclosures. Actual results and outcomes could differ significantly from our estimates, judgments, and assumptions. Significant estimates, judgments, and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, fair value of assets acquired and liabilities assumed for business combinations, useful lives and realizability of long-lived assets including our goodwill and intangible assets, income tax reserves, and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. The effects of material revisions in estimates are reflected in the condensed consolidated financial statements in the period of change and prospectively from the date of the change in estimate. </span></div><div style="margin-bottom:12pt;text-indent:27pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The ongoing global COVID-19 pandemic has adversely impacted many operational aspects of our business and may continue to do so in the future. Since the start of the pandemic, we have assessed the impact that COVID-19 had on our results of operations, including, but not limited to an assessment of our allowance for credit losses, the carrying value of short-term and long-term marketable securities, the carrying value of goodwill and other long-lived assets, and the impact to revenue recognition and cost of revenues. The future impacts of the pandemic and any resulting economic impact are largely unknown and are continuing to evolve. We will continue to actively monitor the impact that COVID-19 has on the results of our business operations, and may make decisions required by federal, state or local authorities, or that are determined to be in the best interests of our employees, customers, partners, suppliers and stockholders. As a result, our estimates and judgments may change materially as new events occur or additional information becomes available to us.</span></div>
	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	<div style="margin-bottom:12pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Concentrations of Credit Risk</span></div><div style="margin-bottom:12pt;text-indent:27pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash, cash equivalents, marketable securities, and accounts receivable. The primary focus of our investment strategy is to preserve capital and meet liquidity requirements. Our investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. To manage the risk exposure, we invest cash equivalents and marketable securities in a variety of fixed income securities, including government and investment-grade debt securities and money market funds. We place our cash primarily in checking and money market accounts with reputable financial institutions. Deposits held with these financial institutions may exceed the amount of insurance provided on such deposits, if any.</span></div><div style="margin-bottom:12pt;text-indent:27pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which we make substantial sales. Our customer base consists of a large number of geographically dispersed customers diversified across several industries. To reduce this risk, we routinely assess the financial strength of our customers. Based on such assessments, we believe that our accounts receivable credit risk exposure is limited. </span></div>No customer accounted for more than 10% of revenue for the three and six months ended June 30, 2021. One customer accounted for 13% and 12% of revenue for the three and six months ended June 30, 2020. As of June 30, 2021, we had one customer that accounted for more than 10% of the total accounts receivable balance. As of December 31, 2020, we had a different customer that accounted for more than 10% of the total accounts receivable balance.
CY2021Q2	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	85026000	USD
CY2020Q2	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	74663000	USD
	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	169878000	USD
	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	137587000	USD
CY2021Q2	fsly	Enterprise Customer Threshold EnterpriseCustomerThreshold	100000	USD
CY2021Q2	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	85026000	USD
CY2020Q2	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	74663000	USD
	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	169878000	USD
	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	137587000	USD
	us-gaap	Revenue Performance Obligation Description Of Payment Terms RevenuePerformanceObligationDescriptionOfPaymentTerms	Payment terms on invoiced amounts are at an average of 30 days.
CY2021Q2	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	209000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	387000	USD
CY2021Q2	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	27236000	USD
CY2020Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	18020000	USD
CY2021Q2	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	6840000	USD
CY2020Q2	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	834000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	11136000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	301000	USD
CY2021Q2	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	134700000	USD
CY2021Q2	us-gaap	Revenue Remaining Performance Obligation Percentage RevenueRemainingPerformanceObligationPercentage	0.84
CY2021Q2	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P12M
CY2021Q2	us-gaap	Capitalized Contract Cost Amortization Period CapitalizedContractCostAmortizationPeriod	P5Y
CY2021Q2	us-gaap	Capitalized Contract Cost Net Noncurrent CapitalizedContractCostNetNoncurrent	22077000	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Net Noncurrent CapitalizedContractCostNetNoncurrent	19332000	USD
CY2021Q2	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1500000	USD
CY2020Q2	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	800000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	2900000	USD
	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1500000	USD
CY2021Q2	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	687986000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	62900000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	241744000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities Current AvailableForSaleSecuritiesDebtSecuritiesCurrent	131283000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Securities Noncurrent AvailableForSaleSecuritiesDebtSecuritiesNoncurrent	173227000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities Noncurrent AvailableForSaleSecuritiesDebtSecuritiesNoncurrent	20448000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	414971000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	151731000	USD
CY2021Q2	fsly	Cash Cash Equivalents And Debt Securities Available For Sale CashCashEquivalentsAndDebtSecuritiesAvailableForSale	1102957000	USD
CY2020Q4	fsly	Cash Cash Equivalents And Debt Securities Available For Sale CashCashEquivalentsAndDebtSecuritiesAvailableForSale	214631000	USD
CY2021Q2	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	415091000	USD
CY2021Q2	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	11000	USD
CY2021Q2	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	131000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	414971000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	151626000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	110000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	5000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	151731000	USD
CY2021Q2	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Number Of Positions DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions	0	security
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Number Of Positions DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions	0	security
CY2021Q2	us-gaap	Cash Equivalents At Carrying Value CashEquivalentsAtCarryingValue	682214000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	414971000	USD
CY2021Q2	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	980000	USD
CY2021Q2	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	1098165000	USD
CY2020Q4	us-gaap	Cash Equivalents At Carrying Value CashEquivalentsAtCarryingValue	41627000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	151731000	USD
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	980000	USD
CY2020Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	194338000	USD
CY2020	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	313665000	USD
CY2020	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	-159248000	USD
CY2021Q2	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	190849000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	157632000	USD
CY2021Q2	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	74378000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	61653000	USD
CY2021Q2	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	116471000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	95979000	USD
CY2021Q2	us-gaap	Depreciation Depreciation	6900000	USD
CY2020Q2	us-gaap	Depreciation Depreciation	4700000	USD
	us-gaap	Depreciation Depreciation	13300000	USD
	us-gaap	Depreciation Depreciation	9400000	USD
CY2021Q2	us-gaap	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	51800000	USD
CY2020Q4	us-gaap	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	36200000	USD
CY2021Q2	us-gaap	Finance Lease Right Of Use Asset Accumulated Amortization FinanceLeaseRightOfUseAssetAccumulatedAmortization	9100000	USD
CY2020Q4	us-gaap	Finance Lease Right Of Use Asset Accumulated Amortization FinanceLeaseRightOfUseAssetAccumulatedAmortization	6700000	USD
CY2021Q2	us-gaap	Capitalized Contract Cost Net Noncurrent CapitalizedContractCostNetNoncurrent	22077000	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Net Noncurrent CapitalizedContractCostNetNoncurrent	19332000	USD
CY2021Q2	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	893000	USD
CY2020Q4	us-gaap	Restricted Cash Noncurrent RestrictedCashNoncurrent	893000	USD
CY2021Q2	us-gaap	Other Assets Miscellaneous Noncurrent OtherAssetsMiscellaneousNoncurrent	4608000	USD
CY2020Q4	us-gaap	Other Assets Miscellaneous Noncurrent OtherAssetsMiscellaneousNoncurrent	4692000	USD
CY2021Q2	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	27578000	USD
CY2020Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	24917000	USD
CY2021Q2	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	11539000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	17840000	USD
CY2021Q2	us-gaap	Sales And Excise Tax Payable Current SalesAndExciseTaxPayableCurrent	6885000	USD
CY2020Q4	us-gaap	Sales And Excise Tax Payable Current SalesAndExciseTaxPayableCurrent	6274000	USD
CY2021Q2	fsly	Accrued Acquisition Related Costs AccruedAcquisitionRelatedCosts	0	USD
CY2020Q4	fsly	Accrued Acquisition Related Costs AccruedAcquisitionRelatedCosts	3644000	USD
CY2021Q2	fsly	Accrued Colocation And Bandwidth Costs AccruedColocationAndBandwidthCosts	4135000	USD
CY2020Q4	fsly	Accrued Colocation And Bandwidth Costs AccruedColocationAndBandwidthCosts	2208000	USD
CY2021Q2	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	6050000	USD
CY2020Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	4368000	USD
CY2021Q2	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	28609000	USD
CY2020Q4	us-gaap	Accrued Liabilities Current AccruedLiabilitiesCurrent	34334000	USD
CY2021Q2	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	22667000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	15916000	USD
CY2021Q2	fsly	Accrued Computer And Networking Equipment AccruedComputerAndNetworkingEquipment	6249000	USD
CY2020Q4	fsly	Accrued Computer And Networking Equipment AccruedComputerAndNetworkingEquipment	3126000	USD
CY2021Q2	fsly	Liability For Early Exercised Stock Options Current LiabilityForEarlyExercisedStockOptionsCurrent	255000	USD
CY2020Q4	fsly	Liability For Early Exercised Stock Options Current LiabilityForEarlyExercisedStockOptionsCurrent	255000	USD
CY2021Q2	us-gaap	Other Sundry Liabilities Current OtherSundryLiabilitiesCurrent	564000	USD
CY2020Q4	us-gaap	Other Sundry Liabilities Current OtherSundryLiabilitiesCurrent	380000	USD
CY2021Q2	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	29735000	USD
CY2020Q4	us-gaap	Other Liabilities Current OtherLiabilitiesCurrent	19677000	USD
CY2021Q2	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	4569000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	2104000	USD
CY2021Q2	fsly	Accrued Payroll Taxes Noncurrent Cares Act AccruedPayrollTaxesNoncurrentCARESAct	1676000	USD
CY2020Q4	fsly	Accrued Payroll Taxes Noncurrent Cares Act AccruedPayrollTaxesNoncurrentCARESAct	1676000	USD
CY2021Q2	us-gaap	Other Sundry Liabilities Noncurrent OtherSundryLiabilitiesNoncurrent	257000	USD
CY2020Q4	us-gaap	Other Sundry Liabilities Noncurrent OtherSundryLiabilitiesNoncurrent	620000	USD
CY2021Q2	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	6502000	USD
CY2020Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	4400000	USD
	fsly	Subleases Remaining Lease Terms SubleasesRemainingLeaseTerms	P3Y
CY2021Q2	us-gaap	Sublease Income SubleaseIncome	200000	USD
CY2020Q2	us-gaap	Sublease Income SubleaseIncome	300000	USD
	us-gaap	Sublease Income SubleaseIncome	400000	USD
	us-gaap	Sublease Income SubleaseIncome	500000	USD
CY2021Q2	us-gaap	Operating Lease Cost OperatingLeaseCost	6452000	USD
CY2020Q2	us-gaap	Operating Lease Cost OperatingLeaseCost	5227000	USD
	us-gaap	Operating Lease Cost OperatingLeaseCost	12804000	USD
	us-gaap	Operating Lease Cost OperatingLeaseCost	10162000	USD
CY2021Q2	us-gaap	Variable Lease Cost VariableLeaseCost	1460000	USD
CY2020Q2	us-gaap	Variable Lease Cost VariableLeaseCost	1355000	USD
	us-gaap	Variable Lease Cost VariableLeaseCost	2818000	USD
	us-gaap	Variable Lease Cost VariableLeaseCost	2288000	USD
CY2021Q2	fsly	Operating Variable And Short Term Lease Costs OperatingVariableAndShortTermLeaseCosts	7912000	USD
CY2020Q2	fsly	Operating Variable And Short Term Lease Costs OperatingVariableAndShortTermLeaseCosts	6582000	USD
	fsly	Operating Variable And Short Term Lease Costs OperatingVariableAndShortTermLeaseCosts	15622000	USD
	fsly	Operating Variable And Short Term Lease Costs OperatingVariableAndShortTermLeaseCosts	12450000	USD
CY2021Q2	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	1250000	USD
CY2020Q2	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	723000	USD
	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	2484000	USD
	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	1408000	USD
CY2021Q2	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	405000	USD
CY2020Q2	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	149000	USD
	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	735000	USD
	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	268000	USD
CY2021Q2	fsly	Finance Lease Cost FinanceLeaseCost	1655000	USD
CY2020Q2	fsly	Finance Lease Cost FinanceLeaseCost	872000	USD
	fsly	Finance Lease Cost FinanceLeaseCost	3219000	USD
	fsly	Finance Lease Cost FinanceLeaseCost	1676000	USD
CY2021Q2	us-gaap	Operating Lease Payments OperatingLeasePayments	6491000	USD
CY2020Q2	us-gaap	Operating Lease Payments OperatingLeasePayments	4141000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	12856000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	8413000	USD
CY2021Q2	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	405000	USD
CY2020Q2	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	149000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	735000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	268000	USD
CY2021Q2	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	3628000	USD
CY2020Q2	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1307000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	6579000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	2900000	USD
CY2021Q2	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	4657000	USD
CY2020Q2	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	7898000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	13481000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	10278000	USD
CY2021Q2	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	13529000	USD
CY2020Q2	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	5852000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	15538000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	7842000	USD
CY2021Q2	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P4Y4M24D
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P4Y5M8D
CY2021Q2	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P2Y4M20D
CY2020Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P2Y6M3D
CY2021Q2	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0556
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0568
CY2021Q2	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.0514
CY2020Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.0512
CY2021Q2	fsly	Lessee Operating Lease Lease Not Yet Commenced Commitment Amount LesseeOperatingLeaseLeaseNotYetCommencedCommitmentAmount	17800000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Payments Remainder Of Fiscal Year LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear	24489000	USD
CY2021Q2	us-gaap	Finance Lease Liability Payments Remainder Of Fiscal Year FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear	8403000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	19354000	USD
CY2021Q2	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	15014000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	13941000	USD
CY2021Q2	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	11488000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	12374000	USD
CY2021Q2	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	1675000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	11864000	USD
CY2021Q2	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	0	USD
CY2021Q2	fsly	Lessee Operating Lease Liability To Be Paid After Year Four LesseeOperatingLeaseLiabilityToBePaidAfterYearFour	11900000	USD
CY2021Q2	fsly	Finance Lease Liability To Be Paid After Year Four FinanceLeaseLiabilityToBePaidAfterYearFour	0	USD
CY2020Q4	us-gaap	Intangible Assets Gross Excluding Goodwill IntangibleAssetsGrossExcludingGoodwill	127398000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	93922000	USD
CY2021Q2	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	36580000	USD
CY2021Q2	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	9252000	USD
CY2021Q2	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	2122000	USD
CY2021Q2	us-gaap	Operating Lease Liability OperatingLeaseLiability	84670000	USD
CY2021Q2	us-gaap	Finance Lease Liability FinanceLeaseLiability	34458000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	635590000	USD
	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	56000	USD
CY2021Q2	us-gaap	Goodwill Goodwill	635646000	USD
CY2021Q2	us-gaap	Intangible Assets Gross Excluding Goodwill IntangibleAssetsGrossExcludingGoodwill	129491000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	16276000	USD
CY2021Q2	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	113215000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	5656000	USD
CY2020Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	121742000	USD
CY2021Q2	us-gaap	Payments To Acquire Intangible Assets PaymentsToAcquireIntangibleAssets	2100000	USD
	us-gaap	Payments To Acquire Intangible Assets PaymentsToAcquireIntangibleAssets	2100000	USD
CY2021Q2	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	5300000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	10600000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	100000	USD
CY2020Q2	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	100000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear	10628000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	20974000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	19874000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	19040000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	16561000	USD
CY2021Q2	fsly	Finite Lived Intangible Assets Amortization Expense After Year Four FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFour	25770000	USD
CY2021Q2	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	112847000	USD
CY2020Q4	us-gaap	Line Of Credit LineOfCredit	20300000	USD
CY2020Q4	fsly	Cash Collateral For Line Of Credit CashCollateralForLineOfCredit	70100000	USD
CY2021Q2	us-gaap	Interest Expense Debt InterestExpenseDebt	1000000.0	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	1400000	USD
CY2020Q2	us-gaap	Interest Expense Debt InterestExpenseDebt	400000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	700000	USD
CY2021Q2	us-gaap	Purchase Obligation Future Minimum Payments Remainder Of Fiscal Year PurchaseObligationFutureMinimumPaymentsRemainderOfFiscalYear	33931000	USD
CY2021Q2	us-gaap	Purchase Obligation Due In Next Twelve Months PurchaseObligationDueInNextTwelveMonths	34839000	USD
CY2021Q2	us-gaap	Purchase Obligation Due In Second Year PurchaseObligationDueInSecondYear	13663000	USD
CY2021Q2	us-gaap	Purchase Obligation Due In Third Year PurchaseObligationDueInThirdYear	2592000	USD
CY2021Q2	us-gaap	Purchase Obligation Due In Fourth Year PurchaseObligationDueInFourthYear	1642000	USD
CY2021Q2	fsly	Purchase Obligation Due After Fourth Year PurchaseObligationDueAfterFourthYear	46000	USD
CY2021Q2	us-gaap	Purchase Obligation PurchaseObligation	86713000	USD
CY2021Q2	us-gaap	Sales And Excise Tax Payable Current And Noncurrent SalesAndExciseTaxPayableCurrentAndNoncurrent	6900000	USD
CY2020Q4	us-gaap	Sales And Excise Tax Payable Current And Noncurrent SalesAndExciseTaxPayableCurrentAndNoncurrent	6300000	USD
CY2020Q3	fsly	Loss Contingency Pending Claims Number Consolidated LossContingencyPendingClaimsNumberConsolidated	2	lawsuit
CY2020Q3	us-gaap	Loss Contingency Pending Claims Number LossContingencyPendingClaimsNumber	1	lawsuit
CY2019Q2	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000.0	shares
CY2019Q2	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.00002
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2021Q2	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2021Q2	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	6963000	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	5.63
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P6Y8M12D
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	569094000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	0
	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	1029000	shares
	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	5.45
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	184000	shares
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	10.48
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	5750000	shares
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	5.51
	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P6Y1M6D
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	310997000	USD
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	4054000	shares
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	4.03
	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P5Y6M
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	225285000	USD
CY2021Q2	fsly	Share Based Compensation Arrangement By Share Based Payment Award Options Unvested Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsUnvestedExercisableNumber	216000	shares
CY2021Q2	fsly	Share Based Compensation Arrangement By Share Based Payment Award Options Unvested Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsUnvestedExercisableWeightedAverageExercisePrice	6.54
	fsly	Share Based Compensation Arrangement By Share Based Payment Award Options Unvested Exercisable Weighted Average Remaining Contractual Term ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsUnvestedExercisableWeightedAverageRemainingContractualTerm	P7Y3M18D
CY2021Q2	fsly	Share Based Compensation Arrangement By Share Based Payment Award Options Unvested Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsUnvestedExercisableAggregateIntrinsicValue	11483000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	60900000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	76300000	USD
	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested In Period Fair Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1	8800000	USD
	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested In Period Fair Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1	4600000	USD
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2020Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Accelerated Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost	1200000	USD
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Accelerated Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost	1200000	USD
CY2021Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Plan Modification Incremental Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost	1100000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Plan Modification Incremental Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost	1100000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Accelerated Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost	400000	USD
CY2020Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Accelerated Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost	400000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Plan Modification Incremental Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost	300000	USD
CY2020Q2	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Plan Modification Incremental Compensation Cost ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost	300000	USD
CY2021Q2	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions	18700000	USD
CY2021Q2	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares	62248	shares
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares	90977	shares
CY2021Q2	fsly	Amount Withheld In Contributions For Employee Stock Purchase Plan AmountWithheldInContributionsForEmployeeStockPurchasePlan	2600000	USD
	fsly	Amount Withheld In Contributions For Employee Stock Purchase Plan AmountWithheldInContributionsForEmployeeStockPurchasePlan	6000000.0	USD
CY2020Q2	fsly	Amount Withheld In Contributions For Employee Stock Purchase Plan AmountWithheldInContributionsForEmployeeStockPurchasePlan	1900000	USD
	fsly	Amount Withheld In Contributions For Employee Stock Purchase Plan AmountWithheldInContributionsForEmployeeStockPurchasePlan	4100000	USD
CY2021Q2	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	200000	shares
	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	200000	shares
	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	200000	shares
CY2020Q2	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	200000	shares
CY2021Q2	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	33426000	USD
CY2020Q2	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	16281000	USD
	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	64264000	USD
	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	22610000	USD
CY2021Q2	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	400000	USD
	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	800000	USD
CY2020Q2	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	400000	USD
	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	600000	USD
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	20470000	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	13747000	shares
CY2021Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-200000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-0.0	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	0.0	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	800000	USD
	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	1	segment
CY2021Q2	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	116471000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	95979000	USD

Files In Submission

Name	View Source	Status
0001517413-21-000154-index-headers.html	Edgar Link	pending
0001517413-21-000154-index.html	Edgar Link	pending
0001517413-21-000154.txt	Edgar Link	pending
0001517413-21-000154-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
fsly-20210630.htm	Edgar Link	pending
fsly-20210630.xsd	Edgar Link	pending
fsly-20210630_cal.xml	Edgar Link	unprocessable
fsly-20210630_def.xml	Edgar Link	unprocessable
fsly-20210630_htm.xml	Edgar Link	completed
fsly-20210630_lab.xml	Edgar Link	unprocessable
fsly-20210630_pre.xml	Edgar Link	unprocessable
fsly-63021x10qexhibit311.htm	Edgar Link	pending
fsly-63021x10qexhibit312.htm	Edgar Link	pending
fsly-63021x10qexhibit321.htm	Edgar Link	pending
fsly-63021x10qexhibit322.htm	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
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report.css	Edgar Link	pending
Show.js	Edgar Link	pending

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$FSLY
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2021 Q2 Form 10-Q Financial Statement

#000151741321000154 Filed on August 06, 2021

Income Statement

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Facts In Submission

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$FSLY Fastly Inc Stock $fsly

2021 Q2 Form 10-Q Financial Statement

#000151741321000154 Filed on August 06, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$FSLY
Fastly Inc Stock $fsly