| Cover | Aug. 04, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 4, 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 |
