| Cover | May 05, 2021 | Nov. 09, 2020 |
| Cover [Abstract] | ||
| Document Type | 8-K | |
| Document Period End Date | May 5, 2021 | |
| Entity Registrant Name | FALCONSTOR SOFTWARE, INC. | |
| Entity Tax Identification Number | 77-0216135 | |
| Entity File Number | 000-23970 | |
| Entity Incorporation, State or Country Code | DE | |
| Entity Address, Postal Zip Code | 78701 | |
| Entity Address, State or Province | TX | |
| Entity Address, City or Town | Austin | |
| Entity Address, Address Line Two | Suite 400 | |
| Entity Address, Address Line One | 701 Brazos Street | |
| City Area Code | 631 | |
| Local Phone Number | 777-5188 | |
| Entity Central Index Key | 0000922521 | |
| Amendment Flag | false | |
| Written Communications | false | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Entity Emerging Growth Company | false |
