| Document and Entity Information | Dec. 17, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | TechTarget Inc |
| Amendment Flag | false |
| Entity Central Index Key | 0001293282 |
| Document Type | 8-K |
| Document Period End Date | Dec. 17, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-33472 |
| Entity Tax Identification Number | 04-3483216 |
| Entity Address, Address Line One | 275 Grove Street |
| Entity Address, City or Town | Newton |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02466 |
| City Area Code | (617) |
| Local Phone Number | 431-9200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.001 par value per share |
| Trading Symbol | TTGT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
