| Cover | Oct. 18, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 18, 2021 |
| Entity File Number | 001-35521 |
| Entity Registrant Name | CLEARSIGN TECHNOLOGIES CORPORATION |
| Entity Central Index Key | 0001434524 |
| Entity Tax Identification Number | 26-2056298 |
| Entity Incorporation, State or Country Code | WA |
| Entity Address, Address Line One | 12870 Interurban Avenue South |
| Entity Address, City or Town | Seattle |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98168 |
| City Area Code | 206 |
| Local Phone Number | 673-4848 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | CLIR |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
