| Extension | File Description |
| .RBR | Uncommon Files |
| .RBRES | Uncommon Files |
| .RBS | Audio Files |
| .RBT | Data Files |
| .RBU | Uncommon Files |
| .RBV | Uncommon Files |
| .RBVCP | Developer Files |
| .RBW | Uncommon Files |
| .RBX | Executable Files |
| .RBXL | Game Files |
| .RBXM | Game Files |
| .RBY | Uncommon Files |
| .RBZ | Uncommon Files |
| .RC | Developer Files |
| .RC0 | Uncommon Files |
| .RC1 | Uncommon Files |
| .RC2 | System Files |
| .RC3 | Uncommon Files |
| .RC4 | Uncommon Files |
| .RC5 | Uncommon Files |
| .RC6 | Uncommon Files |
| .RC7 | Uncommon Files |
| .RC8 | Uncommon Files |
| .RC9 | Uncommon Files |
| .RCA | Uncommon Files |
| .RCB | Uncommon Files |
| .RCC | Uncommon Files |
| .RCD | Data Files |
| .RCE | Uncommon Files |
| .RCF | Settings Files |
| .RCG | Data Files |
| .RCH | Uncommon Files |
| .RCI | Uncommon Files |
| .RCJ | Uncommon Files |
| .RCK | Uncommon Files |
| .RCL | Disk Image Files |
| .RCM | Uncommon Files |
| .RCN | Uncommon Files |
| .RCO | System Files |
| .RCP | Uncommon Files |
| .RCPROFILE | Text Files |
| .RCPROJECT | Video Files |
| .RCQ | Uncommon Files |
| .RCR | Uncommon Files |
| .RCS | 3D Image Files |
| .RCT | Settings Files |
| .RCU | Uncommon Files |
| .RCV | Uncommon Files |
| .RCW | Uncommon Files |
| .RCX | Data Files |
| .RCY | Audio Files |
| .RCZ | Uncommon Files |
| .RC_ | Uncommon Files |
| .RD | Uncommon Files |
| .RD0 | Uncommon Files |
| .RD1 | Uncommon Files |
| .RD2 | Uncommon Files |
| .RD3 | Uncommon Files |
| .RD4 | Uncommon Files |
| .RD5 | Uncommon Files |
| .RD6 | Uncommon Files |
| .RD7 | Uncommon Files |
| .RD8 | Uncommon Files |
| .RD9 | Uncommon Files |
| .RDA | Game Files |
| .RDATA | Data Files |
| .RDB | Video Files |
| .RDC | GIS Files |
| .RDD | Uncommon Files |
| .RDE | Uncommon Files |
| .RDEF | Uncommon Files |
| .RDF | Disk Image Files |
| .RDG | Uncommon Files |
| .RDH | Uncommon Files |
| .RDI | Settings Files |
| Extension | File Description |
| .RDIALOG | Uncommon Files |
| .RDJ | Uncommon Files |
| .RDK | Uncommon Files |
| .RDL | Vector Image Files |
| .RDM | Uncommon Files |
| .RDN | Uncommon Files |
| .RDO | Settings Files |
| .RDP | Settings Files |
| .RDPROJ | Uncommon Files |
| .RDQ | Uncommon Files |
| .RDR | Uncommon Files |
| .RDS | 3D Image Files |
| .RDT | Uncommon Files |
| .RDU | Uncommon Files |
| .RDV | Uncommon Files |
| .RDW | Uncommon Files |
| .RDX | Data Files |
| .RDY | Uncommon Files |
| .RDZ | Uncommon Files |
| .RE | Uncommon Files |
| .RE0 | Uncommon Files |
| .RE1 | Uncommon Files |
| .RE2 | Uncommon Files |
| .RE3 | Uncommon Files |
| .RE4 | Uncommon Files |
| .RE5 | Uncommon Files |
| .RE6 | Uncommon Files |
| .RE7 | Uncommon Files |
| .RE8 | Uncommon Files |
| .RE9 | Uncommon Files |
| .REA | Uncommon Files |
| .READ | Uncommon Files |
| .READM | Uncommon Files |
| .README | Text Files |
| .README1ST | Uncommon Files |
| .READS | Uncommon Files |
| .REALDOWNLO | Uncommon Files |
| .REB | Uncommon Files |
| .REC | Video Files |
| .RECEIVE | Uncommon Files |
| .RECON | Uncommon Files |
| .RECORDS | Uncommon Files |
| .RED | CAD Files |
| .RED-DWARF | Uncommon Files |
| .REDSECTOR | Uncommon Files |
| .REDUCTION | Uncommon Files |
| .REE | Uncommon Files |
| .REF | GIS Files |
| .REFER | Uncommon Files |
| .REFERENCE | Data Files |
| .REG | System Files |
| .REGENT | Uncommon Files |
| .REGET | Uncommon Files |
| .REGISTER | Uncommon Files |
| .REGULAR | Uncommon Files |
| .REH | Uncommon Files |
| .REI | Uncommon Files |
| .REID | Uncommon Files |
| .rej | Uncommon Files |
| .REK | Uncommon Files |
| .REKO | Uncommon Files |
| .REL | Data Files |
| .RELEASE | Uncommon Files |
| .RELEASENS | Uncommon Files |
| .REM | Misc Files |
| .REMI | Uncommon Files |
| .REMINDER | Uncommon Files |
| .REMINDERS | Uncommon Files |
| .REMIX | Uncommon Files |
| .REMOVE | Uncommon Files |
| .REN | Uncommon Files |
| .REO | Uncommon Files |
| .REP | Game Files |
| .REPAIRS | Uncommon Files |
| .REPL | Uncommon Files |
