| gas | Atari Jaguar GPU Assembly Source |
| gb | Basic4GL Source Code |
| gb1 | Game Maker Backup File |
| gb2 | Game Maker Backup File |
| gbas | GLBasic Source Code |
| gbf | BASIS GUIBuilder Control Data |
| gbk | Embarcadero InterBase Database Backup |
| gbl | Visual Basic Global Declaration |
| gc1 | Golden Common Lisp 1.1 Source Code |
| gcda | Gcov Data File |
| gcg | GAUSS Compiled Program |
| gch | Precompiled C Header File |
| gcl | GNU Common Lisp Source Code |
| gcna | Gcov Compiled Output |
| gcno | Gcov Metadata File |
| gcob | TRANSFER Cobol Source Code |
| gcov | GNU GCOV Logfile |
| gcr | GlowCode Profiling Results |
| gd | Godot Engine Source Code |
| gdb | Embarcadero InterBase Database File |
| gdt | Graph Drawing Toolkit Output |
| gek | GECK/Papyrus Script Editor Script |
| gemspec | RubyGems Gem Specification |
| genmodel | Eclipse Modeling Framework GenModel Data |
| gex | GameMaker Studio Extension |
| gf | Grammatical Framework Source |
| gfa | GFA BASIC Tokenized Source |
| gfar | Greenfoot Scenario Archive |
| gfe | Grammatical Framework Example |
| gfm | GitHub Flavored Markdown Document |