| hld | Structural Desktop Hold Data |
| hlg | BMERC Homolog Format Data |
| hli | Halcyon NSS License File |
| hlog | VMware ESXi Host Log |
| hlq | ESO-MIDAS Help Data |
| hlt | Hyperlynx Thermal Data |
| hlw | Hioki Logger Communicator Waveform Data |
| hlx | Multi-Edit Help Data |
| hlx | Hollex Cartridge Image |
| hl_ | Compressed HLP File |
| hm4 | Lorex Client Backup Data |
| hmb | SPEEDTRONIC Mark IV HMI Bridge |
| hme | Smartphone Home Screen Theme |
| hmf | ANSYS Fluent Metafile |
| hmf | HOOPS Metafile |
| hmg | modhmm HMG model |
| hmm | HMMER Data |
| hmo | ROXIE Mesh Information |
| hmskin | Help and Manual Skin Data |
| hmt | HighMAT File |
| hnd | HNSKY Deep Sky Database |
| hnr | iGO Primo Defined Routes |
| hns | Hallo Northern Sky Data |
| ho | Knowledge Explorer Hierarchy Outline |
| hob | CARIS Hydrographic Object Binary Data |
| hobo | Onset HOBO Data Logger Data |
| hol | Microsoft Outlook Holiday Data |
| hom | PLINK Homozygosity Data |
| hor | Heliosoft AttriGenPlus Input Horizon File |
| hph | Designer Graphics System 2 Data |
| hpr | Adobe RoboHelp Internal Data |
| hprof | Java Hprof Data |
| hps | HP Digital Sender Information |
| hpx | MetaVR 3D Model |
| hpz | Helpinator Zipped Archive |
