| hid2 | KeepSafe Data |
| hif | Quicken Online Data |
| hik | OptiTrack MotionBuilder MarkerSet Data |
| hin | HyperChem Data |
| his | FindinSite Database |
| hisf | DL_POLY Formatted History File |
| hist | MicroStrategy History Data |
| history | Eclipse IDE Local History Data |
| hisu | DL_POLY Unformatted History File |
| hix | PageTech PCLTool Low Level Index File |
| hk | ASCA GIS Housekeeping Data |
| hkdb | iTunes Music Library |
| hkf | Microsoft .NET Install Hook File |
| hkh | HTML-Kit Help File |
| hkl | SHELX Reflection Data |
| hkm | Havok Movie File |
| hkp | Mentor Graphics HKP Database |
| hkt | Havok Tagfile |
| hkx | Havok XML Model File |
| hl | HeuristicLab Storage |
| hl7 | HL7 Standard Format Data |
| hlb | HP OpenVMS Help Library |
| hlc | ESO-MIDAS Help Command Data |
| hld | Structural Desktop Hold Data |
| hlg | BMERC Homolog Format Data |
| hli | Halcyon NSS License File |
| hln | Bentley MicroStation Hidden Line Data |
| hlog | VMware ESXi Host Log |
| hlq | ESO-MIDAS Help Data |
| hlt | Hyperlynx Thermal Data |
| hlw | Hioki Logger Communicator Waveform Data |
| hlx | Hollex Cartridge Image |
| hlx | Multi-Edit Help Data |
| hl_ | Compressed HLP File |
| hm4 | Lorex Client Backup Data |