| 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 |
| htd | HyperTRANSCRIBE Document |
| htext | WebKNotes HTXT Document |
| htm | Hypertext Markup Language Document |
| htmhjt | Treepad v6 Text Database |
| html | Hypertext Markup Language Document |
| htx | Extended HTML Template |
| htxt | WebKNotes HTXT Document |
| hus | Husqvarna Viking Embroidery Design |
| hvs | Cubicon Cubicreator G-Code |
| hwp | Hangul Word Processor Document |
| hwpx | Hangul Word Processor 2010 Document |
| hxl | Microsoft Help 2 Registered Namespace List |
| hxn | Hexagon 3D Model |
| hxs | MS Help 2 Compiled Help |
| hyp | Adobe Acrobat Spelling Dictionary |
| hype | Hype Document |
| hypetemplate | Hype Document Template |
| hyy | HiTi Photo Desiree v2 Template |
| hz | Chinese Hanzi Text File |
| i4d | Inform4 Document |
| iam | Autodesk Inventor Assembly Model |
| iba | Lectra Clothing Design Pieces Document |
