| .L64 | Commodore International | Asetustiedostot | 64LAN Image File | Unknown Software | Unknown Developer |
| .LARGE | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LASXML | Unknown Developer | Datatiedostot | Laser App Data Exchange | Unknown Software | Unknown Developer |
| .LAUNCHER | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LBB | Unknown Developer | Harvinaiset Tiedostot | Liberty Bible DataBase File | Unknown Software | Unknown Developer |
| .LBR | Dag Agren, Circlesoft | Pakatut tiedostot | LU Library Archive | LU file archiver | Unknown Developer |
| .LDC | Unknown Developer | Harvinaiset Tiedostot | Steuer 2001 File | Steuer2001 | Unknown Developer |
| .LDH | Unknown Developer | Harvinaiset Tiedostot | Uncommon File Extension | Unknown Software | Unknown Developer |
| .LDN | Unknown Developer | Harvinaiset Tiedostot | Uncommon File Extension | Unknown Software | Unknown Developer |
| .LDS | GNU Project | Sovelluskehittäjän tiedostot | Binutils LD Linker Script | Unknown Software | Unknown Developer |
| .LEA | Unknown Developer | Harvinaiset Tiedostot | Unknown File Type | Unknown Software | Unknown Developer |
| .LED | Sony | Asetustiedostot | Sony AIBO LED Lights Control Data | Unknown Software | Unknown Developer |
| .LES | David A. Wheeler | Datatiedostot | Lesson File | Unknown Software | Unknown Developer |
| .LEXT | Olympus Corporation | Datatiedostot | Olympus Lext Measurement Export | Unknown Software | Unknown Developer |
| .LG | Unknown Developer | Pakatut tiedostot | Arhangel Compressed Archive | Unknown Software | Unknown Developer |
| .LGF | Microsoft Corporation | Datatiedostot | Microsoft Windows Application Log File | Unknown Software | Unknown Developer |
| .LHD | Unknown Developer | Tekstitiedostot | Label Home Document File | Label Home | Unknown Developer |
| .LHP | Electric Butterfly, Inc. | Datatiedostot | Lighthouse Organizer Data | Lighthouse Organizer | Unknown Developer |
| .LIB | Various Developers | Datatiedostot | Generic Data Library | Unknown Software | Unknown Developer |
| .LIM | Unknown Developer | Pakatut tiedostot | Limit Compressed Data | Unknown Software | Unknown Developer |
| .LISTING | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LIZ | Unknown Developer | Pakatut tiedostot | Compressed List File | Unknown Software | Unknown Developer |
| .LI_ | Unknown Developer | Harvinaiset Tiedostot | Rukus File | Unknown Software | Unknown Developer |
| .LKH | Unknown Developer | Harvinaiset Tiedostot | Worm.Generic.LKH Virus File | Unknown Software | Unknown Developer |
| .LKU | STMicroelectronics | Suoritettavat tiedostot | ST Microelectronics Linked Unit Data | Unknown Software | Unknown Developer |
| .LLF | Unknown Developer | Datatiedostot | IITM Local Language Data | IITM | Unknown Developer |
| .LNT | Gimpel Software | Sovelluskehittäjän tiedostot | PC-lint/FlexeLint Configuration File | Laego Visual Manager Live | Unknown Developer |
| .LNV | Unknown Developer | Harvinaiset Tiedostot | Uncommon File Extension | Unknown Software | Unknown Developer |
| .LOAD | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LOADER | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LOAN | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LOGO | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LOJ | Unknown Developer | Harvinaiset Tiedostot | Uncommon File Extension | Unknown Software | Unknown Developer |
| .LOW | Digital Equipment Corporation | Järjestelmätiedostot | PDP-10 Low Segment Of A Two-segment Program | Unknown Software | Unknown Developer |
| .LP1 | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .LPI | Unknown Developer | Datatiedostot | Laser Printer Information | Unknown Software | Unknown Developer |
| .LPS | DAZ 3D | 3D-kuvatiedostot | Bryce Leaf Shape File | Unknown Software | Unknown Developer |
| .LQC | Unknown Developer | Harvinaiset Tiedostot | Unknown File Type | Unknown Software | Unknown Developer |
| .LQR | Europoe Space Agency (ESA) | Pakatut tiedostot | LBR Library File | LBR library software | Unknown Developer |
| .LSW | Technics | Asetustiedostot | Technics Keyboard Current Panel File | Unknown Software | Unknown Developer |
| .LSZ | Unknown Developer | 3D-kuvatiedostot | Learning Score Zip File | Learning Score | Unknown Developer |
| .LU | ThoughtWing, LLC | Harvinaiset Tiedostot | ThoughtWing Library Unit File | Unknown Software | Unknown Developer |
| .LVH | Unknown Developer | Harvinaiset Tiedostot | Unknown File Type | Unknown Software | Unknown Developer |
| .LVX | Unknown Developer | Harvinaiset Tiedostot | Unknown File Type | Unknown Software | Unknown Developer |
| .LYB | Unknown Developer | Harvinaiset Tiedostot | Unknown File Type | Unknown Software | Unknown Developer |
| .LYZ | Unknown Developer | Harvinaiset Tiedostot | Uncommon File Extension | Unknown Software | Unknown Developer |
| .LZW | Unknown Developer | Pakatut tiedostot | LZW Compressed Archive File | Unknown Software | Unknown Developer |
| .LZZZZZZZ | Apple | Datatiedostot | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
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