| h1h | Microsoft Help Merged Hierarchy File |
| h1k | Microsoft Help Keywords Index |
| h1q | Microsoft Help Merged Query Index |
| h1s | Microsoft Help Compiled Help Data |
| h1t | Microsoft Help Topic Definition |
| h1v | Microsoft Help VTopic Definition |
| h1w | Microsoft Help Merged Keyword Index |
| h2d | Hydrus-2D Data File |
| h2drumkit | Hydrogen Drum Kit Data |
| h2song | Hydrogen Drum Notes Data |
| h2w | H2testw Data |
| h323 | H.323 IP Telephony Data |
| h3b | Line 6 POD HD300 Edit Bundle |
| h3d | HyperView 3D Model |
| h3e | Line 6 POD HD300 Edit Preset Data |
| h4 | Hierarchical Data Format File |
| h4b | Line 6 POD HD400 Edit Bundle |
| h4e | Line 6 POD HD400 Edit Preset Data |
| h5 | Hierarchical Data Format Release 5 |
| h5b | Line 6 POD HD500 Edit Bundle |
| h5e | Line 6 POD HD500 Edit Preset Data |
| h5s | Line 6 POD HD500 Edit Setlist Data |
| h77t | GEODAS MGD77T Header Data |
| h86 | CP/M Data |
| hal | HotDocs Answer Library |
| halog | IEInspector HTTP Analyzer Log |
| hamachi | Hamachi Client Data |
| har | HTTP Archive |
| har | E-Sword Harmony Resource |
| harx | E-Sword v9.1 Harmony Resource |
