| 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 |
| rdy | TSP-INet Server Acknowledge Data |
| rdz | RemoteDocs Encrypted Document |
| re1 | Hy-Tek Meet Manager Registration Data |
| re2 | NEK5000 Re2file |
| re3 | Honeywell HNDR-S4824 Backup Data |
| re4 | RomEditor4 Binary Data |
| rea | NEK5000 Reafile |
| readyboot | ReadyBoot Data |
| real | Gnome Desktop Data |
| reality | RealityKit 3D Scene |
| reals | ScadaWorks Real Bank Template |
| reapeaks | REAPER Media Peak Information |
| reapindex | REAPER Media Peak Index |
| rec | Easy CD Creator Recovery Data |
| rec | Epidata Data File |
| rec | Medlin Payroll Software Bank Reconciliation Data |
| rec | Recogniform ICR Data File |
| rec | Windows 3.1 Macro Recorder Data |
| rech | 4D Database for Mac Search Document |
| reco | EverNote Reco Data |
| red | CARE-S InfoWorks Rainfall Data |
| red | IBM Rational Rose Module Diagram |
| redif | ReDIF Template |
| redis | Redis Database |
| ref | Ad-Aware Signature Data |
| ref | PLINK Long-format Reference Allele File |
| ref | RFSCAT Simulator Wind Field Reference Data |
| ref | WinPLOTR Refined Parameters Data |
| reference | Budget In Brief Reference Data |
| refx | E-Sword Reference Library Note Data |
