| ls8 | Lumion v8 Scene |
| lsg3x | LinSig 3 Document |
| ltm | IBM Lotus Forms Document |
| ltx | LaTeX Document |
| luf | Lipikar Uniform Format Document |
| lums | SAP Lumira Document |
| lumx | SAP Lumira Discovery 2.0 Document |
| lvw | Livewire Document |
| lwl | Lightwright Printed Paperwork Formatting Instructions |
| lwo | Lightwave 3D Object |
| lwob | Lightwave 3D Object |
| lwp | Lotus Word Pro Document |
| lws | Lightwave 3D Scene |
| lwsc | Lightwave 3D Scene |
| lxe | Luxology Modo 3D Scene |
| lxf | LEGO Digital Designer Model |
| lxfml | LEGO Digital Designer Model |
| lxo | Luxology Modo 3D Image |
| ly | GNU Lilypond Document |
| lyc | bestIMAGE Compressed Design |
| lyr | bestIMAGE Layer Data |
| lyt | Proteus Electronics Layout |
| lyx | LyX Document |
| m15 | thinEdge M15 File |
| ma | Mathematica ASCII File |
| ma | Autodesk Maya 3D ASCII Scene |
| ma2 | Winplot Mapping Document |
| maf | Microsoft Access Form |
| mag | Microsoft Access Diagram Shortcut |
| maj | Autodesk Fabrication Job |
| makerbot | MakerBot 3D Print Document |
| mam | Microsoft Access Macro |
| man | Unix Manual Page |
| manu | Lotus Manuscript v1 Document |
| maq | Microsoft Access Query |