| r | Pegasus Mail Resource File |
| r | REBOL Source Code |
| radius | Ruby-Radius Script |
| rake | Rake File |
| raml | RESTful API Modeling Language Document |
| rap | RAPTOR Data |
| rapp | Ride7 Application |
| rb | RealBasic Source Code |
| rb | Ruby Console Application |
| rbc | Rembo-C Script Source |
| rbe | RealView Debugger Connection Properties |
| rbj | XRK Compiled Redcode Object File |
| rbm | RealBasic Menu |
| rbw | Ruby Windowed Application |
| rbx | Rembo-C Compiled Executable |
| rc | Visual Studio Resource Script |
| rc2 | Visual Studio RC2 Resource |
| rct | VS Resource Script Template |
| rda | R Data File |
| rdata | R Workspace |
| rdcl | Report Designer Client Report Definition |
| rdf | ProWorx NXT Cross-reference Data |
| rdk | BlackBerry RIM Development Key |
| rdlc | Visual Studio Client Report Definition Document |
| rdoc | Ruby RDoc Document |
| re | Python Regular Expressions Source Code |
| re | Reason Module |
| reb | REBOL Source Code |
| red | XRK Redcode Source Code |
| regmap | Altera Quartus II Register Map Information |
| rei | Reason Module Interface |
| rel | Retrieve 4GL Dataset |
| reloc | Windows PE Relocation Section |
| rep | WinDev HyperFileSQL REP File |
| res | Windows Resource File |
