| grdb | GRAMPS Database |
| gre | GRETEP Data |
| greenshot | Greenshot Data |
| grfx | GraphStudioNext XML Graph Data |
| grh | ILWIS Graphs Data |
| gri | Petrosys Grid Data |
| grib | Gridded Binary Data |
| grid | GridMove Grid Template |
| grk | Gradekeeper Class Gradebook |
| grldr | GRUB4DOS Internal Loader Data |
| grm | PLINK GCTA Text Relationship Matrix |
| group | Unix Filesystem Group Quota Data |
| groups | WebMoney Keeper CLASSIC Group Data |
| grov | Reason Regroove Data |
| growlregdict | Growl Registration Ticket Data |
| growlticket | Growl Notification Data |
| grp | GenePattern Gene Set Group File |
| grp | GameExchange2 Scene List |
| grph | GRPH Data File |
| grr | Gradekeeper Class Roster |
| grs | Getright Skin |
| grt | Grapher Template |
| gru | FXpansion GURU Preset |
| grv | Microsoft Office Groove File |
| grv | PTC Creo Mill Grooving Parameter Data |
| grv | CART Grove Data |
| grx | Getright Exported List |
| grxml | XML Grammar File |
| gs | GemStone Document |
| gs-bck | Genius Scan Backup Data |
| gs1 | Genecyst Emulator Saved State |
| gs2 | Genecyst Emulator Saved State |
| gs3 | GameStarter File |
| gs3 | Genecyst Emulator Saved State |
| gs4 | Genecyst Emulator Saved State |