| Abbreviation | Definition |
|---|---|
| HST | Handmade Software Graphics histogram (HSI raw file) |
| HST | History |
| HT | Data (HyperTerminal) |
| HTA | HTML Application |
| HTM | HyperText Markup Language document |
| HTML | HyperText Markup Language document |
| HTMLS | HyperText Markup Language document with Server-side include |
| HTT | HyperText Template |
| HTX | HTML template (MS FrontPage) |
| HWD | Hollywood software Presentation file |
| HWD | Presentation (Hollywood) |
| HX | THOR database Cross-reference Hsh file |
| HXM | Alternate Protocol Selection menu for all users (Procomm Plus) |
| HXX | C++ header |
| HY1 | Hyphenation algorithms (Ventura Publisher) |
| HY2 | Hyphenation algorithms (Ventura Publisher) |
| HYC | Data (WordPerfect) |
| HYD | Hyphenation dictionary (WordPerfect for Win) |
| HYP | Compressed file archive (Hyper) |
| HYP | Hyphenation InDesign Proximity Dictionary Adobe |