| cmc | Comic Collector Collection Data |
| cmd5 | CrystalMaker V5 Data File |
| cmdb | CFX Mesh Database |
| cmdf | CrystalMaker V2 Data File |
| cmdl | Cafu Engine Model Data |
| cmdrw | CET Designer Drawing Data |
| cmdt | ClarisWorks Dictionary Data |
| cmf | CIFMIF File |
| cmf | PBD-14 CMF Data |
| cmfav | CET Designer Favorites Data |
| cmfrl | CET Designer Furniture Layout Data |
| cmh | PLINK Cochran Mantel Haenszel 2x2xK Test Report |
| cmh2 | PLINK Cochran Mantel Haenszel IxJxK Test Report |
| cmj | ControlMyJoystick Profile |
| cml | CryptoMailer Encrypted File |
| cml | Chemical Markup Language File |
| cmlast | CET Designer Last Drawing Backup |
| cmlock | CET Designer Lock Data |
| cmm | Corel Multimedia Manager v7 Album |
| cmmtheme | CleanMyMac Theme Data |
| cmn | Microsoft SMS Collection Membership Update |
| cmo3 | Live2D Cubism 3 Model Data |
| cmod | Celestia Model |
| cmp | General CADD Component Data |
| cmp | Heliosoft Seismaster Colormap File |
| cmp | KiCad Parts-to-module Assignments Data |
| cmp7 | Araxis Merge Comparison Data |
| cmp7 | Araxis Merge Saved Comparison Data |
| cmpck | CET Designer Pack and Go Data |
| cmpd | Chemnum Compounds Data |