| Document and Entity Information | 12 Months Ended |
| Dec. 31, 2020 | |
| Cover page. | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 6, 2020 |
| Entity Registrant Name | TRANSACT TECHNOLOGIES INC |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 0-21121 |
| Entity Tax Identification Number | 06-1456680 |
| Entity Address, Address Line One | One Hamden Center |
| Entity Address, Address Line Two | 2319 Whitney Avenue, Suite 3B |
| Entity Address, City or Town | Hamden |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06518 |
| City Area Code | 203 |
| Local Phone Number | 859-6800 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001017303 |
| Title of 12(b) Security | Common stock, par value $0.01 per share |
| Trading Symbol | TACT |
| Security Exchange Name | NASDAQ |
