| his | WRAP Hydrologic Index Series Data |
| hisf | DL_POLY Formatted History File |
| hist | MicroStrategy History Data |
| history | Eclipse IDE Local History Data |
| hisu | DL_POLY Unformatted History File |
| hive | Apache Hive Data |
| hix | PageTech PCLTool Low Level Index File |
| hjson | HJSON Format Data |
| hk | ASCA GIS Housekeeping Data |
| hk5 | Act! HK5 Database |
| hkdb | iTunes Music Library |
| hkf | Microsoft .NET Install Hook File |
| hkh | HTML-Kit Help File |
| hkl | RMCProfile H K L Range Data |
| hkl | SHELX Reflection Data |
| hkm | Havok Movie File |
| hkp | Mentor Graphics HKP Database |
| hkt | Havok Tagfile |
| hkx | Havok XML Model File |
| hl | HeuristicLab Storage |
| hl6 | HorizontalLog 6 Data |
| hl7 | HL7 Standard Format Data |
| hlb | HP OpenVMS Help Library |
| hlc | ESO-MIDAS Help Command Data |
| hld | Structural Desktop Hold Data |
| hlf | FAR Manager Help Data |
| hlg | BMERC Homolog Format Data |
| hli | Halcyon NSS License File |
| hli | Tekla Structural High Level Interface Data |
| hlm | 3DCS Contributor Analysis Data |
