| hhh | Power C Precompiled Header |
| hhk | HTML Help Index |
| hi | Haskell Interface |
| hic | HicEst Script |
| hie | GHC HI Extended |
| hiro | ARToolKit Hiro Marker Data |
| hj | Habanero-Java Source Code |
| hkk | HTML Help AutoIndex |
| hks | HTML-Kit Script |
| hla | High Level Assembly Source Code |
| hlsl | Microsoft DirectX D3D High Level Shader Language |
| hm | WinHelp Context ID |
| hoc | HOC Script |
| hpack | Haskell Package |
| hpf | High Performance Fortran Source Code |
| hpp | C++ Header File |
| hpw | CompuServe Home Page Wizard Document |
| hql | Apache Hive HiveQL Script |
| hrl | Erlang Header File |
| hs | Haskell Source |
| hsdl | Hierarchical Scan Description Language Data |
| hse | Homesite Snippet End |
| hsh | Visual Studio HShader Data |
| hshader | Visual Studio HShader Data |
| hsm | Assembly Header File |
| hsp | WinDev HyperFileSQL Stored Procedure |
| hss | Homesite Snippet Start |
| htl | HTL Source |
| htp | htp Source File |
| hx | Haxe Source Code |
| hxa | MS Help 2 Project Attribute Definition |
| hxc | MS Help 2 Project Collection Definition |
| hxe | MS Help 2 Project Sample Definition |
| hxf | MS Help 2 Project Include File |
| hxk | MS Help 2 Project Index |