| cit | BibExcel Cited Document |
| ckd | Kubotek KeyCreator Design Container |
| ckt | CircuitMaker Document |
| cl2doc | Comic Life 2 Document |
| cl2lyt | Comic Life 2 Layout |
| cl2tpl | Comic Life 2 Document Template |
| cl3 | Easy CD Creator 3 Cover Layout |
| clarify | Clarify Document |
| clgx | Collage Maker Collage |
| clkb | Clicker Books |
| clkbd | Clicker Board Set |
| clkd | Clicker Docs |
| clkt | Clicker Template |
| clkw | Clicker Word Bank |
| clkx | Clicker Grid Set |
| cln | scanGogh I Scan Document |
| clt | cdrLabel Template |
| cmdx | Clinical Map Document Based on XML |
| cmk | CardShop Plus Document |
| cmp | Chord Pro Chord |
| cmp | HotDocs Component File |
| cmp | Label Designer Plus Document |
| cmp | Solid Edge Wire Harness Design |
| cmp_xml | Solid Edge Wire Harness Design XML |
| cmx | Corel Presentations Exchange Document |
| cnd | ControlDraw Diagram |
| cndx | Avery DesignPro for Mac Document |
| cnt | Windows Help Content |
| co | Cult3D Object |
| cob | Caligari TrueSpace Object |
| coc | BibExcel Co-occurrence Document |
| col | HTML Help Collection |
| comic | Comic Life v1.2 Document |
| comicdoc | Comic Life v1.3 Document |
| comiclife | Comic Life Document |