| rb | Ruby Console Application |
| rbc | Rembo-C Script Source |
| rbe | RealView Debugger Connection Properties |
| rbj | XRK Compiled Redcode Object File |
| rbm | RealBasic Menu |
| rbo | RealBasic Class |
| rbw | Ruby Windowed Application |
| rbx | Rembo-C Compiled Executable |
| rc | Visual Studio Resource Script |
| rc2 | Visual Studio RC2 Resource |
| rc3 | Visual Studio Visual C Resource Data |
| rct | VS Resource Script Template |
| rda | R Data File |
| rdata | R Workspace |
| rdbg | RemedyBG Debugger Data |
| 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 |
| rdoff | NASM Relocatable Dynamic Object File Format Data |
| rdv | NTgraph Borland C 32 Data |
| re | Python Regular Expressions Source Code |
| re | Reason Module |
| reb | REBOL Source Code |
| red | Modula-2 Path Info |
| red | XRK Redcode Source Code |
| reflector | .NET Reflector Data |
| refresh | Visual Studio Refresh Data |
| regi | Kagi Registration Module Data |
| regmap | Altera Quartus II Register Map Information |
| rei | Reason Module Interface |
| rel | PDP-10 Relocatable Object |
| rel | Retrieve 4GL Dataset |
| reloc | Windows PE Relocation Section |
