ClearSign Technologies (CLIR) - Prospectus

As filed with the Securities and Exchange Commission on August 12, 2025 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 CLEARSIGN TECHNOLOGIES CORPORATION (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) Delaware 3823 26-2056298 (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Identification No.) 8023 East ...