XML 9 R1.htm IDEA: XBRL DOCUMENT v3.21.4
Cover - shares
 9 Months Ended
Sep. 30, 2021
Aug. 19, 2021
Cover [Abstract]    
Document Type 10-Q/A  
Amendment Flag false  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Sep. 30, 2021  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2021  
Current Fiscal Year End Date --12-31  
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  
Title of 12(b) Security Common Stock  
Trading Symbol CLIR  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   31,482,454