Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 28, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	0-23970
Entity Registrant Name	FALCONSTOR SOFTWARE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0216135
Entity Address, Address Line One	701 Brazos Street, Suite 400
Entity Address, City or Town	Austin
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78701
City Area Code	631
Local Phone Number	777-5188
Title of 12(g) Security	Common Stock, $0.001 par value
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Documents Incorporated by Reference	The information required by Part III of Form 10-K will be incorporated by reference to certain portions of a definitive proxy statement which is expected to be filed by the Company pursuant to Regulation 14A within 120 days after the close of its fiscal year.
Entity Central Index Key	0000922521
Amendment Flag	false
Entity Public Float			$ 1,526,052
Entity Common Stock, Shares Outstanding		5,949,463
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020