| .R8 | Unknown Developer | Ficheiros Raw de Câmera | RAW Graphics File | Unknown Software | Unknown Developer |
| .R8P | Unknown Developer | Ficheiros de Fonte | Font File | Unknown Software | Unknown Developer |
| .RA1 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RADIOREVOL | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RAINDROPPI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RASTERW | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RAW_PPM | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RAZ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RBH | RBH Access | Ficheiros de Sistema | RBH Access Technologies Firmware | Unknown Software | Unknown Developer |
| .RBN | Richard Pavlicek | Ficheiros de Jogo | Richard’s Bridge Notation File | Unknown Software | Unknown Developer |
| .RCE | Unknown Developer | Uncommon Files | NTgraph GUI Control 3D File | Unknown Software | Unknown Developer |
| .RCM | Faithlife | Ficheiros de Dados | Logos Library System Verse Map | Unknown Software | Unknown Developer |
| .RCPROFILE | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RDB-SHM | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RDB2 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .READ | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REALDOWNLO | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RECOVERYDA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .REFER | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .REG | Microsoft Corporation | Ficheiros de Sistema | Registry File | Unknown Software | Unknown Developer |
| .REGDUMP | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .REGISTER | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .REL | Nintendo | Ficheiros de Jogo | Relocatable Module File | Stage Switcher | Unknown Developer |
| .RELEASE | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REMOVE | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REN | Unknown Developer | Uncommon Files | Renamed File | Unknown Software | Unknown Developer |
| .REP?FB_XD_FRAGMENT= | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .REPORTS | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REQU | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REQUEST | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REQW | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RESONANCEI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RESOURCESC | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RESPECT | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .RETURNTOOL | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .REUNION | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REVE | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REWARD | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .REZCODE | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .RFC1896 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RFM | Beatnik | Ficheiros de Áudio | Rich Music Format File | Unknown Software | Unknown Developer |
| .RFX | Unknown Developer | Ficheiros de Dados | TouchStar License | Unknown Software | Unknown Developer |
| .RGA | Unknown Developer | Ficheiros de Dados | Residual Gas Analyzer Data File | Unknown Software | Unknown Developer |
| .RGB | Silicon Graphics, Inc. | Ficheiros de Imagem Raster | RGB Bitmap | Unknown Software | Unknown Developer |
| .RGBA | Silicon Graphics, Inc. | Ficheiros de Imagem Raster | Silicon Graphics Image File Format | Unknown Software | Unknown Developer |
| .RGH | Unknown Developer | Ficheiros Gráficos | ZZ RouGH Image | Unknown Software | Unknown Developer |
| .RGR | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RHT | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RIA | Unknown Developer | Ficheiros de Imagem Raster | Alpharel Group IV Raster Graphics File | Unknown Software | Unknown Developer |
| .RIDEOFVALK | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RII | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RKP | Devolutions | Ficheiros de Configurações | RemoteKeys Profile File | Unknown Software | Unknown Developer |
| .RLELZW | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .RLO | Unknown Developer | Ficheiros de Dados | Basic Realizer Careal Library File | Unknown Software | Unknown Developer |
| .RLU | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .ROADS | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .ROUT | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .ROUTINES | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .RPSS | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RPST | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RPTDOCUMEN | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RPTTEMPLAT | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RPU | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RQZ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RTI | Interscape | Ficheiros de Áudio | Real Tracker Instrument File | Real Tracker | Unknown Developer |
| .RTM | Unknown Developer | Ficheiros de Áudio | Real Tracker Module | Real Tracker | Unknown Developer |
| .RTS | Heaventools Software | Ficheiros de Desenvolvedor | Resource Tuner Console Script | Real Tracker | Unknown Developer |
| .RTV | NewTek | Ficheiros de Vídeo | NewTek Uncompressed Video Data | Unknown Software | Unknown Developer |
| .RU) | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .RV2 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .RVP | Sharp Electronics | Ficheiros de Sistema | Sharp Blu-ray Player Firmware File | Unknown Software | Unknown Developer |
| .RWJ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
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