| rda | Oracle Database Storage Area |
| rdat | RNA Data |
| rdb | Oracle Database Root |
| rdbx | RiScan Pro Point Cloud Data |
| rdc | CYANA Residual Dipolar Coupling Restraint File |
| rdd | IBM Informix Genero Studio Data Schema |
| rdf | Reaction Data File |
| rdh | Siemens MR Spectroscopy Header Data |
| rdi | SPEFO Differential Spectrum Data |
| 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 |
| rek | Fraunhofer EZRT Volume Data |
| rel | PLINK Text Relationship Matrix |
| rel | my Knowledge Relation Data |
| renderman | RenderMan Data |
| renv | Rhino 3D Saved Environment Data |
| rep | Act! Report Data |
| repx | XtraReports Report Definition |