| Extension | File Description |
| .REPORT | Uncommon Files |
| .REPORTING | Uncommon Files |
| .REPORTS | Uncommon Files |
| .REPT | Uncommon Files |
| .REPX | Uncommon Files |
| .REQ | Misc Files |
| .REQU | Uncommon Files |
| .REQUEST | Uncommon Files |
| .REQUEST1 | Uncommon Files |
| .REQUEST2 | Uncommon Files |
| .RER | Uncommon Files |
| .RES | Developer Files |
| .RES11 | Uncommon Files |
| .RESCUE | Uncommon Files |
| .RESID | Uncommon Files |
| .RESIDENT2 | Uncommon Files |
| .RESONANCEI | Uncommon Files |
| .RESOURCE | Uncommon Files |
| .RESOURCES | Developer Files |
| .RESOURCESC | Uncommon Files |
| .RESPECT | Uncommon Files |
| .RESTORE | Uncommon Files |
| .RESX | Developer Files |
| .RET | Data Files |
| .RETRNTOOLS | Uncommon Files |
| .RETURNTOOL | Uncommon Files |
| .REU | Uncommon Files |
| .REUNION | Uncommon Files |
| .REV | Compressed Files |
| .REV1 | Uncommon Files |
| .REV5 | Uncommon Files |
| .REVALVER | Uncommon Files |
| .REVE | Uncommon Files |
| .REVENGE | Uncommon Files |
| .REVHIST | Uncommon Files |
| .REVIEW | Uncommon Files |
| .REVISION | Uncommon Files |
| .REW | Uncommon Files |
| .REWARD | Uncommon Files |
| .REX | Audio Files |
| .REXX | Uncommon Files |
| .REY | Uncommon Files |
| .REZ | Game Files |
| .REZCODE | Uncommon Files |
| .REZEQUS | Uncommon Files |
| .REZREF | Uncommon Files |
| .RF | Uncommon Files |
| .RF0 | Uncommon Files |
| .RF1 | Uncommon Files |
| .RF2 | Uncommon Files |
| .RF3 | Uncommon Files |
| .RF4 | Uncommon Files |
| .RF5 | Uncommon Files |
| .RF6 | Uncommon Files |
| .RF7 | Uncommon Files |
| .RF8 | Uncommon Files |
| .RF9 | Uncommon Files |
| .RF? | Data Files |
| .RFA | Data Files |
| .RFB | Misc Files |
| .RFC | Uncommon Files |
| .RFC1896 | Uncommon Files |
| .RFD | Game Files |
| .RFE | Uncommon Files |
| .RFF | Uncommon Files |
| .RFG | Uncommon Files |
| .RFH | Uncommon Files |
| .RFI | Uncommon Files |
| .RFJ | Uncommon Files |
| .RFK | Uncommon Files |
| .RFL | Audio Files |
| .RFM | Game Files |
| .RFN | Misc Files |
| .RFO | Data Files |
| .RFORK | Uncommon Files |
| Extension | File Description |
| .RFP | Misc Files |
| .RFQ | Uncommon Files |
| .RFR | Uncommon Files |
| .RFS | Uncommon Files |
| .RFT | 3D Image Files |
| .RFU | Uncommon Files |
| .RFV | Uncommon Files |
| .RFW | Uncommon Files |
| .RFX | Uncommon Files |
| .RFY | Uncommon Files |
| .RFZ | Uncommon Files |
| .RG | Uncommon Files |
| .RG0 | Uncommon Files |
| .RG1 | Uncommon Files |
| .RG2 | Uncommon Files |
| .RG3 | Uncommon Files |
| .RG4 | Uncommon Files |
| .RG5 | Uncommon Files |
| .RG6 | Uncommon Files |
| .RG7 | Uncommon Files |
| .RG8 | Uncommon Files |
| .RG9 | Uncommon Files |
| .RGA | Uncommon Files |
| .RGB | Raster Image Files |
| .RGBA | Uncommon Files |
| .RGC | Uncommon Files |
| .RGD | Uncommon Files |
| .RGE | Data Files |
| .RGF | Uncommon Files |
| .RGG | Uncommon Files |
| .RGH | Uncommon Files |
| .RGI | Uncommon Files |
| .RGJ | Uncommon Files |
| .RGK | Uncommon Files |
| .RGL | Uncommon Files |
| .RGLR | Uncommon Files |
| .RGM | Uncommon Files |
| .RGN | GIS Files |
| .RGO | Data Files |
| .RGP | Game Files |
| .RGQ | Uncommon Files |
| .RGR | Uncommon Files |
| .RGS | Executable Files |
| .RGT | Uncommon Files |
| .RGU | Uncommon Files |
| .RGV | Uncommon Files |
| .RGW | Uncommon Files |
| .RGX | Uncommon Files |
| .RGY | Uncommon Files |
| .RGZ | Uncommon Files |
| .RH | Uncommon Files |
| .RH0 | Uncommon Files |
| .RH1 | Uncommon Files |
| .RH2 | Uncommon Files |
| .RH3 | Uncommon Files |
| .RH4 | Uncommon Files |
| .RH5 | Uncommon Files |
| .RH6 | Uncommon Files |
| .RH7 | Uncommon Files |
| .RH8 | Uncommon Files |
| .RH9 | Uncommon Files |
| .RHA | Uncommon Files |
| .RHB | Uncommon Files |
| .RHC | Uncommon Files |
| .RHD | Uncommon Files |
| .RHE | Uncommon Files |
| .RHF | Uncommon Files |
| .RHG | Uncommon Files |
| .RHH | Uncommon Files |
| .RHI | Uncommon Files |
| .RHJ | Uncommon Files |
| .RHK | Uncommon Files |
| .RHL | Uncommon Files |
| .RHM | Uncommon Files |
| .RHN | Uncommon Files |
