| rbt | Lego Mindstorms NXT Program |
| rbw | Real Studio Window Data |
| Ruby Windowed Application |
| rbx | Rembo-C Compiled Executable |
| Ruby Script |
| rc | Visual Studio Resource Script |
| rc2 | Visual Studio RC2 Resource |
| rc3 | Visual Studio Visual C Resource Data |
| rcs | RAD Studio Compiled RCS Output |
| rct | VS Resource Script Template |
| rcv | Xilinx ISE FPGA Editor Recovery Data |
| rda | R Data File |
| rdata | R Workspace |
| rdbg | RemedyBG Debugger Data |
| rdcl | Report Designer Client Report Definition |
| rdef | Geoworks UI Resource Data |
| 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 |
| Reason Module |
| reb | REBOL Source Code |
| red | Modula-2 Path Info |
| XRK Redcode Source Code |
| reds | Red/System Source Code File |
| 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 |
| rej | Mercurial Reject Data |
| rel | PDP-10 Relocatable Object |
| Retrieve 4GL Dataset |
| reloc | Windows PE Relocation Section |
| rem | Delphi Memory Swap Data |
| rep | WinDev HyperFileSQL REP File |
| replit | Replit Project Configuration |
| res | Delphi Localization Data |
| Delphi Resource Data |
| Godot Engine Binary Resource Data |
| Windows Resource File |
| resid | NML Language Compilation Residual Data |
| resjson | Microsoft Edge JavaScript Resources Data |
| resources | Visual Studio .NET Resources Data |
| resx | ASP.NET Resource |
| retro | Retro Forth Source Code |
| rev | LiveCode Plugin |
| rew | WebDev URL Rewriting Data |
| rex | IBM REXX Source Code |
| rexx | IBM REXX Source Code |
| rez | Lithtech Engine Resource File |
| rfx | Modula-2 Software Development System RFX Data |
| rgl | Scarlett Expert System Compiler Rules Data |
| rgs | Windows Registration Script |
| rgss2a | RPG Maker VX RGSS Encrypted Archive |
| rgss3a | RPG Maker VX RGSS Encrypted Archive |
| rgssad | RPG Maker VX RGSS Encrypted Archive |
| rgx | ReaGeniX Code Generator Symbol Table |
| rh | Borland C++ Resource Header |
| rhistory | R History Data |
| rho | Rholang Source Code |
| rhtml | Erubis Script |
| eRuby HTML Web Page |
| rickroll | Rick Roll Source Code |
| ridl | RAD Studio Active X RIDL Data |
| Restricted Interface Definition Language Data |
| rin | Retrieve 4GL Database Index |
| rio | IBM AIX System Data |
| riot | Apache Jena Riotcmd Parser Data |
| rise | RISE Editor Model |
| rjs | Ruby Javascript |
| rkt | Racket Source Code |
| rlib | Rust Compiled Library |
| rll | CA-Realizer RLL File |
| Microsoft Resource Library |
| rln | Alpha Four Field Rules |
| rlz | CA-Realizer Source Code |
