| cle | Icon Lock-iT XP Locked File Indicator |
| clean | Instagram for Android Cache Data |
| clf | DesignWorks Library |
| clf | ListPro Data |
| clf | Source Insight Custom Language Data |
| clf1 | Common Loudspeaker Format Type 1 File |
| clf2 | Common Loudspeaker Format Type 2 File |
| clg | QIP Ignored Contact List Data |
| clh | NoteTab Clip Assistant List |
| cli | AquaCrop Climate Data |
| clib | CATS Library File |
| client | Telepathy Interface Client Data |
| clipping | Mac Text Clipping Data |
| clk | ClickFORMS Data |
| clkc | Clicker Connect Set |
| clkk | Clicker Keyboard |
| clkm | Clicker Matching Set |
| clkp | Clicker Palette |
| clks | Clicker Sentences Data |
| clktk | Clicker Talk Set |
| clkv | Clicker Communicator Vocabulary Set |
| cll | Crick Software Clicker Data |
| clm | Clipboard Master Data |
| clm | GenePattern CEL Descriptor |
| clm | Micrografx Picture Publisher Macro |
| clm2 | Clipboard Master Data |
| clm4 | Clipboard Master Data |
| clmlic | Clipboard Master License Data |
| clo | SPSS Chalkboard Data |
| cloc | CATS Location File |
| clog | SpreadMaster Client Log |
| clonecd | CloneCD Registration Data |
| clonedvd | CloneDVD Registration Data |
| cloud | GOM Atos Point Cloud Data |
| clp | CA-Clipper Compiler Script |
