| lth | Roxio Label Creator Style Data |
| lthmb | Adobe Presenter Audio Thumbnail |
| ltl | TwoTowers LTL Formula |
| ltn | Carlson Survey Lot Network File |
| ltt | HP Library and Tape Tools Log |
| ltz | Poser Light Data |
| ltz | Poser Compressed Light Data |
| luar | UltraDefrag Lua Report |
| lucy | HTC Scribble Note |
| lud | CARE-S InfoWorks Land Use Data |
| lud | ABBYY Lingvo Dictionary User Dictionary |
| luh | ARINC 615A Load Upload Header |
| lum | Luminous Schedule File |
| lup | OzWin Library Update File |
| lup | ARINC 615A Load Upload Part |
| 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 |
| lvix | Lightworks Index File |
| lvlib | LabVIEW Project Library |
| lvlibp | LabVIEW Packed Project Library |
| lvs | Daylon Leveller Selection Mask |
| lw2 | Lightwright Show Data |
| lw3 | Lightwright Show Data |
| lw4 | Lightwright 4 Data |
| lw5 | Lightwright 5 Data |
| lwa | Lightwright Automated Action Data |
| lwac | Likno Web Accordion Builder Data |
| lwav | eXtendable Wad Editor LWAV Data |
| lwbm | Likno Web Button Maker Data |
| lwd | Lightworks Data File |