| lt2 | Poser Light Data |
| lta | Monolith LithTech Game Engine Data |
| ltc | Linguistic Tree Constructor Data |
| ltcx | Linguistic Tree Constructor XML Data |
| ltd | LivingTime Data File |
| ltd | HPE Library and Tape Tools Support Ticket |
| ltf | Frogans Short-cut |
| 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 |
| lu | ThoughtWing Library Unit |
| luar | UltraDefrag Lua Report |
| lucy | HTC Scribble Note |
| lud | CARE-S InfoWorks Land Use Data |
| lud | ABBYY Lingvo Dictionary User Dictionary |
| lum | Luminous Schedule File |
| lup | OzWin Library Update File |
| lvc | Alstom MMS LVC Compiler Report |
| lvd | Avery LabelPro Design Document |
| lve | DanceScore Live Data |
| lvix | Lightworks Index File |
| lvs | Daylon Leveller Selection Mask |
| lw4 | Lightwright 4 Data |
| lw5 | Lightwright 5 Data |
| lwa | Lightwright Automated Action Data |
| lwd | Lightworks Data File |
