File extensions start with character 'R'
| File Type | Category | File Format | |
|---|---|---|---|
| .r | Development Files | Rez Source Code File | |
| .r0 | Compressed Files | WinRAR Compressed Archive | |
| .r00 | Compressed Files | WinRAR Compressed Archive | |
| .r01 | Compressed Files | WinRAR Split Archive Part 1 | |
| .r02 | Compressed Files | WinRAR Split Archive Part 2 | |
| .r03 | Compressed Files | WinRAR Split Archive Part 3 | |
| .r21 | Compressed Files | WinRAR Split Archive Part 21 | |
| .r30 | Compressed Files | WinRAR Split Archive Part 30 | |
| .rad | 3D Graphics Files | VRAD Lights File | |
| .ral | Data Files | WinRail Track Design File | |
| .ram | Audio Files | Real Audio Metadata File | |
| .rar | Compressed Files | WinRAR Compressed Archive | |
| .rat | Partially Downloaded Files | PICS Rating File | |
| .rax | Audio Files | Real Music Store Audio File | |
| .rbc | Backup Files | Retrospect Backup Catalog File | |
| .rbt | Data Files | Lego MINDSTORMS NXT Program | |
| .rbz | Game Files | SketchUp Plug-in | |
| .rcd | Video Files | pcAnywhere Recorded Session File | |
| .rcg | Data Files | Recog Character Recognition Set | |
| .rcx | Data Files | REDCINE-X Project File | |
| .rda | Data Files | R Data File | |
| .rdb | Data Files | N64 ROM Database | |
| .rdx | Data Files | Reflex Data File | |
| .readme | Text Files | Readme File | |
| .reb | Development Files | REBOL Script File | |
| .ref | Data Files | Microsoft Train Simulator Reference File | |
| .reference | Data Files | Budget In Brief Reference File | |
| .reg | Registry Files | Registry File | |
| .regtrans-ms | Windows System Files | Registry Transaction Log File | |
| .rel | Data Files | Norton Internet Security Log File | |
| .rem | Multiple Use Files | BlackBerry Encrypted Data File | |
| .req | Multiple Use Files | SSL Certificate Request File | |
| .res | Development Files | C++ Complied Resource Script | |
| .resx | Development Files | .NET Managed Resources File | |
| .ret | Data Files | BusinessObjects Template | |
| .rez | Game Files | Lithtech Game Engine Resource File | |
| .rf1 | Data Files | Retirement Forecast File | |
| .rfa | Data Files | Revit Family File | |
| .rfd | Page Layout Files | Recogniform Form Designer File | |
| .rfo | Data Files | RoboForm Option File | |
| .rft | 3D Graphics Files | Revit Family Template File | |
| .rge | Data Files | Entourage File Archive | |
| .rgmc | Data Files | RootsMagic Genealogy Project File | |
| .rgo | Data Files | RepliGo File | |
| .rgss2a | Archive Files | RPG Maker VX RGSS Encrypted Archive | |
| .ris | Text Files | Research Information Systems Citation File | |
| .rk | Compressed Files | WinRK File Archive | |
| .rl | Data Files | R.viewer List File | |
| .rm | Digital Video Files | Real Media File | |
| .rmd | Video Files | RED Metadata File | |
| .rmskin | Configuration Files | Rainmeter Skin File | |
| .rmuf | Data Files | Alpha Five Runtime License File | |
| .rmvb | Digital Video Files | RealMedia Variable Bit Rate File | |
| .rmx | Audio Files | RealJukebox Format | |
| .rng | Audio Files | Nokia Composer Ringtone | |
| .rnq | Data Files | Renque Model File | |
| .roca | Data Files | RIB office Compressed Archive | |
| .rod | Data Files | Actuate Report Object Design File | |
| .rog | Data Files | Roger 2 Input Data File | |
| .roi | Data Files | Report Object Instance | |
| .rom | Google Files | N64 Game ROM File | |
| .rou | Data Files | Gerber Route File | |
| .rox | Data Files | Roxio Project File | |
| .roxio | Data Files | Roxio Project | |
| .rp | Data Files | Axure RP Project File | |
| .rpa | Data Files | RIB Project Archive File | |
| .rpd | Data Files | Roleplay Designer Data File | |
| .rpf | Raster Graphics Files | Rich Pixel Format File | |
| .rpm | Package Files | Red Hat Package Manager File | |
| .rpmsg | Multiple Use Files | Outlook Restricted Permission Message | |
| .rpprj | Data Files | Axure RP Shared Project File | |
| .rpprj | Data Files | Reaper Project File | |
| .rpt | Data Files | Crystal Reports File | |
| .rrt | Data Files | Rhapzode Resource Template | |
| .rs | CAD Files | RapidSketch Document | |
| .rsa | Multiple Use Files | RSA Certificate File | |
| .rsc | Data Files | Symbian Application Compiled Resource File | |
| .rsp | Data Files | RSLogix PLC Program File | |
| .rst | Text Files | reStructuredText File | |
| .rsv | Data Files | RSView32 Project File | |
| .rsw | Data Files | R&R SQL Report Writer Report File | |
| .rtd | CAD Files | Robot Structural Analysis Design File | |
| .rte | Compressed Files | RTE Encoded File | |
| .rtf | Text Files | Rich Text Format File | |
| .rtfd | Text Files | Rich Text Format Directory File | |
| .rtp | Data Files | Gromacs Residue Topology Parameter File | |
| .rtx | Text Files | Rich Text Document | |
| .run | Executable Files | Linux Executable File | |
| .rvdata | Data Files | RPG Maker VX Data File | |
| .rvid | Digital Video Files | Snapz Pro X Recorded Video File | |
| .rvt | Data Files | Revit Project File | |
| .rwg | Data Files | Random Word Generator Project File | |
| .rwp | Web Files | RapidWeaver Package | |
| .rws | Data Files | Retina Wireless Scanner File | |
| .rxdata | Data Files | RMXP Data File | |
| .rz | Compressed Files | Rzip Compressed File | |
| .rzb | eBook Files | Red Zion Book File | |
| .rzk | Text Files | File Crypt Password File | |
| .rzn | Text Files | Red Zion Notes File |