| Extension | File Description |
| .CHAT | Web Files |
| .CHATLOG | Uncommon Files |
| .CHB | Uncommon Files |
| .CHC | Uncommon Files |
| .CHD | Game Files |
| .CHE | Uncommon Files |
| .CHEAT | Uncommon Files |
| .CHEATS | Uncommon Files |
| .CHECK | Uncommon Files |
| .CHECKER | Uncommon Files |
| .CHESSREV | Uncommon Files |
| .CHESSTITAN | Game Files |
| .CHF | Uncommon Files |
| .CHG | Data Files |
| .CHGR | Uncommon Files |
| .CHH | Uncommon Files |
| .CHI | Uncommon Files |
| .CHIME | Uncommon Files |
| .CHIMES | Uncommon Files |
| .CHJ | Uncommon Files |
| .CHK | Misc Files |
| .CHKEXP | Uncommon Files |
| .CHKJAIL | Uncommon Files |
| .CHL | Settings Files |
| .CHM | Web Files |
| .CHN | Data Files |
| .CHO | Uncommon Files |
| .CHOICE | Uncommon Files |
| .CHOOCHOO | Uncommon Files |
| .CHOPIN | Uncommon Files |
| .CHOPPER | Uncommon Files |
| .CHOPRO | Uncommon Files |
| .CHOR | Uncommon Files |
| .CHORALE | Uncommon Files |
| .CHORD | Text Files |
| .CHORDHARM | Uncommon Files |
| .CHORDPIANO | Uncommon Files |
| .CHORES | Uncommon Files |
| .CHORUS | Uncommon Files |
| .CHP | Uncommon Files |
| .CHQ | Uncommon Files |
| .CHR | Font Files |
| .CHRISTMAS | Uncommon Files |
| .CHROMAFONT | Uncommon Files |
| .CHRT | Data Files |
| .CHS | System Files |
| .CHT | System Files |
| .CHU | Uncommon Files |
| .CHURCH | Uncommon Files |
| .CHUZZLEDEL | Uncommon Files |
| .CHV | Uncommon Files |
| .CHW | Misc Files |
| .CHX | Settings Files |
| .CHY | Uncommon Files |
| .CHZ | Uncommon Files |
| .CI | System Files |
| .CI0 | Uncommon Files |
| .CI1 | Uncommon Files |
| .CI2 | Uncommon Files |
| .CI3 | Uncommon Files |
| .CI4 | Uncommon Files |
| .CI5 | Uncommon Files |
| .CI6 | Uncommon Files |
| .CI7 | Uncommon Files |
| .CI8 | Uncommon Files |
| .CI9 | Uncommon Files |
| .CIA | Uncommon Files |
| .CIB | Uncommon Files |
| .CIC | Uncommon Files |
| .CID | Uncommon Files |
| .CIDA | Uncommon Files |
| .CIDF | Uncommon Files |
| .CIE | Uncommon Files |
| .CIF | Disk Image Files |
| .CIG | Uncommon Files |
| Extension | File Description |
| .CIH | Uncommon Files |
| .CII | Data Files |
| .CIJ | Uncommon Files |
| .CIK | Uncommon Files |
| .CIL | Vector Image Files |
| .CIM | Uncommon Files |
| .CIN | Raster Image Files |
| .CIN96LM | Uncommon Files |
| .CIN96UPD | Uncommon Files |
| .CIO | Uncommon Files |
| .CIP | Video Files |
| .CIPO | Uncommon Files |
| .CIQ | Uncommon Files |
| .CIR | Uncommon Files |
| .CIRCLES | Uncommon Files |
| .CIS | Uncommon Files |
| .CISO | Uncommon Files |
| .CIT | Raster Image Files |
| .CITY | Uncommon Files |
| .CIU | Uncommon Files |
| .CIV | Uncommon Files |
| .CIV4REPLAY | Uncommon Files |
| .CIV4SAVEDG | Uncommon Files |
| .CIV4WORLDB | Uncommon Files |
| .CIW | Uncommon Files |
| .CIX | Uncommon Files |
| .CIY | Uncommon Files |
| .CIZ | Uncommon Files |
| .CJ0 | Uncommon Files |
| .CJ1 | Uncommon Files |
| .CJ2 | Uncommon Files |
| .CJ3 | Uncommon Files |
| .CJ4 | Uncommon Files |
| .CJ5 | Uncommon Files |
| .CJ6 | Uncommon Files |
| .CJ7 | Uncommon Files |
| .CJ8 | Uncommon Files |
| .CJ9 | Uncommon Files |
| .CJA | Uncommon Files |
| .CJB | Uncommon Files |
| .CJC | Uncommon Files |
| .CJD | Uncommon Files |
| .CJE | Uncommon Files |
| .CJF | Uncommon Files |
| .CJG | Uncommon Files |
| .CJH | Uncommon Files |
| .CJI | Uncommon Files |
| .CJJ | Uncommon Files |
| .CJK | Uncommon Files |
| .CJL | Uncommon Files |
| .CJM | Uncommon Files |
| .CJN | Uncommon Files |
| .CJO | Uncommon Files |
| .CJP | Uncommon Files |
| .CJQ | Uncommon Files |
| .CJR | Uncommon Files |
| .CJS | Uncommon Files |
| .CJT | Uncommon Files |
| .CJU | Uncommon Files |
| .CJV | Uncommon Files |
| .CJW | Uncommon Files |
| .CJX | Uncommon Files |
| .CJY | Uncommon Files |
| .CJZ | Uncommon Files |
| .CK | Uncommon Files |
| .CK0 | Uncommon Files |
| .CK1 | Uncommon Files |
| .CK2 | Uncommon Files |
| .CK3 | Uncommon Files |
| .CK4 | Uncommon Files |
| .CK5 | Uncommon Files |
| .CK6 | Uncommon Files |
| .CK7 | Uncommon Files |
| .CK8 | Uncommon Files |
| .CK9 | Uncommon Files |
