| rgss3a | RPG Maker VX RGSS Encrypted Archive |
| rgssad | RPG Maker VX RGSS Encrypted Archive |
| rh | Borland C++ Resource Header |
| rhistory | R History Data |
| rho | Rholang Source Code |
| rhtml | eRuby HTML Web Page |
| rhtml | Erubis Script |
| ridl | Restricted Interface Definition Language Data |
| rin | Retrieve 4GL Database Index |
| riot | Apache Jena Riotcmd Parser Data |
| rise | RISE Editor Model |
| rjs | Ruby Javascript |
| rkt | Racket Source Code |
| rlib | Rust Compiled Library |
| rll | Microsoft Resource Library |
| rln | Alpha Four Field Rules |
| rlz | CA-Realizer Source Code |
| rmd | R Markdown Source Code |
| rmk | Clipper RMake File |
| rms | Retek Merchandising System Settings |
| rms | JCP Mobile Information Device Profile |
| rmuf | Alpha Five Runtime Users Data |
| rnc | RELAX NG Compact Syntax |
| rng | RELAX NG Syntax File |
| rnw | Sweave Document |
| robo | RoboMind Source Code |
| rodl | RemObjects Definition Language |
| ron | Ron Document |
| rotest | RemObjects SDK Test Data |
| rotestresult | RemObjects SDK Test Results Data |
| rpd | RapidPLUS Application File |
| rpf | ProWorx NXT Cross-reference Pointer |
| rplib | Axure RP Widget Library |
| rpo | GCC Compiler Template Object |
| rpp | FactoryTalk View Studio RecipePlus Component File |