| rat | PICS Service Description |
| raw | Bruker RAW Data |
| rawpkt | Colasoft Capsa Capture Data |
| ra_ | Resco Photo Viewer Thumbnail Cache |
| rbc | Retrospect Backup Catalog |
| rbf | Altera Raw Binary File |
| rbf | RBase Data |
| rbh | Adobe RoboHelp Data |
| rbk | Windows 95 Registry Backup |
| rbl | RegexBuddy Library Data |
| rbm | Tekla Structures Reinforcement Mesh Properties |
| rbn | Richard's Bridge Notation Data |
| rbr | libigl ReAntTweakBar Data |
| rbt | Xilinx Raw BIT Data |
| rbtx | Lego Mindstorms NXT Create Pack and Go File |
| rbuistate | Real Studio UI State Data |
| rbv | GrafNav Exported Binary Values Data |
| rc1 | Samsung S5230 Firmware RSRC1 File |
| rc2 | Samsung S5230 Firmware RSRC2 File |
| rca | RCA Anaesthetic Logbook Document |
| rcb | Ripple Chat Bot Data |
| rcd | Symantec pcAnywhere Recorded Session |
| rcg | Recog Character Recognition Set |
| rch | MODFLOW Recharge Package |
| rch | SWAT Reach Output Data |
| rci | SPEFO Rectified Cleaned Data |
| rcj | Robocopy Job Data |
| rck | REScheck Data |
| rcl | Reflection Command Language Script |
| rcn | QRacing Track Records Data |
