| qtd | Qt Creator Trace Data |
| qvs | QlikView Script |
| qx | Quex Input File |
| qx | Quexal Source Code |
| qxm | Quexal Macro File |
| r | R Source Code |
| r | REBOL Source Code |
| r | Pegasus Mail Resource File |
| 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 |
| rbo | RealBasic Class |
| 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 |
| 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 |