| 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 |
| rdv | NTgraph Borland C 32 Data |
| re | Reason Module |
| re | Python Regular Expressions Source Code |
| 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 |
| resjson | Microsoft Edge JavaScript Resources Data |
| resources | Visual Studio .NET Resources Data |
| resx | ASP.NET Resource |
| rexx | IBM REXX Source Code |
| rgs | Windows Registration Script |
| rgss3a | RPG Maker VX RGSS Encrypted Archive |
| rgssad | RPG Maker VX RGSS Encrypted Archive |
| rh | Borland C++ Resource Header |
| rhtml | eRuby HTML Web Page |
| rhtml | Erubis Script |
