| gtcx | Graitec Exchange Format Document |
| gtemplate | OmniGraffle Template |
| gtp | Guitar Pro Tabulature |
| gtt | Guntrams Tabletweaving Thingy Pattern |
| guide | Amigaguide Hypertext Document |
| gul | JungUm Global Document |
| gv | Graphviz DOT File |
| gvdesign | Gravit Designer Document |
| gwb | GenStat Book |
| gwk | GraphiCode PCB Job |
| gx | Geometry Expressions Document |
| gxd | General CADD Pro Drawing |
| han | Headline Studio Animation |
| hbl | Braille Sense Format File |
| hcdx | Hallmark Card Studio Document |
| hdd | HotDisc Designer Document |
| hdm | Handheld Device Markup Language |
| hdml | Handheld Device Markup Language |
| hdrp | HDRtist Document |
| hdw | Harvard Graphics Drawing |
| heb | DEcomp 3D Scene |
| help | Windows Help File |
| hf | RayShade HeightField Format |
| hfd | HotDocs Form Document |
| hft | HotDocs Envoy-based Form Template |
| hgo | Home Group Overhead Document |
| hht | Help and Support Center HHT |
| hip | Houdini Scene |
| hiplc | Houdini Limited Commercial Scene |
| hipnc | Houdini Apprentice |
| hjt | Treepad v6 Database |
| hlp | Windows Help File |
| hlz | MultiEdit Packed Help File |
| hmk | Hallmark Card Studio Document |
| hmw | Homeword for DeskMate Document |