| hg | Mercurial Data |
| hg | GNOME C++ Header |
| hgdeps | Mercurial Dependencies Data |
| hgignore | Mercurial Ignore Data |
| hgsigs | Mercurial Signatures Data |
| hgsub | Mercurial Subrepo Data |
| hgtags | Mercurial Tags Data |
| hh | HTML Help Header File |
| hh | C++ Header File |
| hhc | HTML Help Table of Contents |
| hhh | Power C Precompiled Header |
| hhk | HTML Help Index |
| hhl | Visual Basic Data |
| hi | Haskell Interface |
| hic | HicEst Script |
| hie | GHC HI Extended |
| hint | Visual C++ Hint Data |
| hiro | ARToolKit Hiro Marker Data |
| hj | Habanero-Java Source Code |
| hkk | HTML Help AutoIndex |
| hks | HTML-Kit Script |
| hl | Haxe Compiler Output |
| hla | High Level Assembly Source Code |
| hlsl | Microsoft DirectX D3D High Level Shader Language |
| hlsli | Microsoft DirectX D3D High Level Shader Language Include |
| hm | WinHelp Context ID |
| hmp | 3D Gamestudio Terrain Data |
| hoc | HOC Script |
| hpack | Haskell Package |
| hpf | High Performance Fortran Source Code |