| 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 |
| hnc | NoteCenter Notes Document |
| hne | NoteCenter Encrypted Notes Document |
| hou | ARCHLine v4 Drawing |
| hp8 | HP NewWave Write Text |
| hpd | HotDocs PDF Document |
| hpl | HotDocs Answer Source |
| hpo | HippoDraw Canvas Document |
| hpt | HotDocs PDF-based Form Template |
| hrx | Herolab E.A.S.Y Document |
| hsf | HOOPS Stream File |
| htc | HTML Component |
