| hwt | Huawei Phone Theme |
| hwv | Hades Waveform Viewer Data |
| hwx | RSNetWorx Registration Data |
| hxb | QCTest Data |
| hxd | Microsoft Help 2 Validator Data |
| hxg | Microsoft Help 2 Filter Cache |
| hxh | Microsoft Help 2 Merged TOC |
| hxi | Microsoft Help 2 Compiled Help Index |
| hxq | Microsoft Help 2 Query Data |
| hxr | Microsoft Help 2 Combined Attribute Index |
| hxw | Microsoft Help 2 Merged Index |
| hy1 | Corel Ventura Publisher Hyphenation Algorithm Data |
| hy2 | Corel Ventura Publisher Hyphenation Algorithm Data |
| hy3 | Hy-Tek Meet Manager Results Data |
| hy3 | Hy-Tek Team Manager Data |
| hyb | HYB Hybrid Data |
| hyc | Corel WordPerfect Internal Data |
| hyd | MARIN Hydrodynamic Database File |
| hyd | WRAP Single Hydrology Data |
| hyp | SmartWare HYP Dictionary Data |
| hyp | HyperLynx BoardSim PCB Layout |
| hyq | CARE-S Depth Hydrographs for Gauged Pipes |
| hyv | Team Manager 1 Meet Setup File |
| hzd | SeisWorks Horizon Datafile |
| hzf | Neosat Fixes |
| hzn | Observer Pro Horizon Data |
| hzs | CrossWorks for ARM Session Data |
| i2b | Invoice2go Product Data |
| i2g | Intergeo I2G Geometric File |
| i3dm | Cesium Instanced 3D Tiles Data |
| i3ml | I3ML Data |
| i5d | IUCLID5 XML Backup |
| i5s | IUCLID5 Compressed Backup |
| i5z | IUCLID5 Export File |
| ia1 | Infinite Algebra 1 Data |