| ltl | DIALux Luminaire Data |
| ltl | TwoTowers LTL Formula |
| ltn | Carlson Survey Lot Network File |
| ltn | LinkTreeNotes Data |
| ltt | HP Library and Tape Tools Log |
| ltz | Poser Compressed Light Data |
| ltz | Poser Light Data |
| lu | ThoughtWing Library Unit |
| luacodec | Reason Remote Lua Codec Data |
| luar | UltraDefrag Lua Report |
| lucidcolorset | Lucid Colorset Data |
| lucs | Amaya Tools Data |
| lucy | HTC Scribble Note |
| lud | ABBYY Lingvo Dictionary User Dictionary |
| lud | Altair FEKO LU-decomposition Data |
| lud | CARE-S InfoWorks Land Use Data |
| lue | Norton LiveUpdate Log |
| luh | ARINC 615A Load Upload Header |
| lum | Luminous Schedule File |
| luminar | Luminar 4 Catalog Database |
| lup | ARINC 615A Load Upload Part |
| lup | OzWin Library Update File |
| lus | ARINC 615A Load Upload Status |
| lux | Spectramap Database |
| luz | Spectramap Data |
| lvc | Alstom MMS LVC Compiler Report |
| lvclass | LabVIEW Class Library |
| lvd | Avery LabelPro Design Document |
| lve | DanceScore Live Data |
| lvg | ListViewGenerator Data |
