| rdic | StarDict Dictionary Resource |
| rdj | JCanyon Texture Data |
| rdml | Real-time PCR Data Markup Language Data |
| rdo | Oracle Database Redo Log |
| rdox | Reflection Desktop Session Data |
| rdr | Dynamic Report Decoder File |
| rdx | Borland Reflex Data File |
| rdy | Ready Pro Accounting Data |
| rdz | RemoteDocs Encrypted Document |
| re2 | NEK5000 Re2file |
| re4 | RomEditor4 Binary Data |
| rea | NEK5000 Reafile |
| real | Gnome Desktop Data |
| rec | Recogniform ICR Data File |
| rec | Windows 3.1 Macro Recorder Data |
| rec | Epidata Data File |
| red | CARE-S InfoWorks Rainfall Data |
| ref | PLINK Long-format Reference Allele File |
| reference | Budget In Brief Reference Data |
| regularizer | SAM Transition Regularizer Data |
| rek | Fraunhofer EZRT Volume Data |
| rel | my Knowledge Relation Data |
| rel | PLINK Text Relationship Matrix |
| renderman | RenderMan Data |
| renv | Rhino 3D Saved Environment Data |
| rep | Act! Report Data |
| repx | XtraReports Report Definition |
| res | Qualitek-4 Results Data |
| res | Abaqus/Standard Restart Data |
| res11 | MIKE 11 DSF Results Data |
