| .KCD | Symantec Corporation | Fişiere de date | Rshiphop.kcd Malware | Kayak | Open Source |
| .KDB | Open Source | Fişiere de baze de date | KeePass Database File | KeePass Password Safe | Open Source |
| .KDBX | Dominik Reichl | Fişiere de date | KeePass Password Database | KeePass Password Safe | Open Source |
| .KDEVELOP | Free Software Foundation | Fişiere de programator | KDevelop Project Data File | KDevelop | Open Source |
| .KDEVPRJ | Free Software Foundation | Fişiere de programator | KDevelop Project File | KDevelop | Open Source |
| .KDS | Knyzhov Dmitry | Fişiere de setări | KD Player Skin File | gVim | Open Source |
| .KEA | Panasonic Corporation | Fişiere de date | Panasonic KTS File | KEALib software | Open Source |
| .KEYSTORE | Oracle Corporation | Fişiere criptate | Java Keystore File | KeyStore Explorer | Open Source |
| .KFI | Unknown Developer | Fişiere de imagini 3D | 3D Forgastest Editor Data | 3D Object Converter | Open Source |
| .KFX | Amazon | Fișere eBook | Amazon KF10 eBook File | Calibre | Open Source |
| .KGB | Open Source | Fişiere comprimate | KGB Archive File | KGB Archiver | Open Source |
| .KHF | Open Source | Fişiere de date | Kwalitan Data File | Kwalitan | Open Source |
| .KHS | Open Source | Fișiere neobișnuite | Kwalitan History Data File | Kwalitan | Open Source |
| .KIWI | Open Source | Fişiere de date | KiwiViewer Scene | KiwiViewer | Open Source |
| .KIX | Ruud Van Velsen | Fişiere executabile | KiXtart Script File | PSPad | Open Source |
| .KMAP | Open Source | Fișiere neobișnuite | LyX Keymap | Lyx | Open Source |
| .KMD | Open Source | Fişiere executabile | ABSTAT For Windows Batch File | ABstat | Open Source |
| .KMF | Open Source | Fişiere de date | Kwalitan Memo File | Kwalitan | Open Source |
| .KML | Keyhole Corporation | Fişiere GIS | Keyhole Markup Language File | Blender (With Google Earth Importer Plugin) | Open Source |
| .KMY | Open Source | Fişiere de date | KMyMoney Data File | KMyMoney | Open Source |
| .KMZ | Google | Fişiere GIS | Google Earth Placemark File | Blender (With Google Earth Importer Plugin) | Open Source |
| .KO | Open Source | Fişiere de sistem | Linux Kernel Module File | Linux | Open Source |
| .KOC | Open Source | Fişiere de date | Koha Offline Circulation Data | Koha | Open Source |
| .KOR | Epic Games | Fişiere de jocuri | Unreal Engine Language Localization | PSPad | Open Source |
| .KPR | Open Source | Fişiere de date | KPresenter Presentation | KOffice | Open Source |
| .KPT | Open Source | Fişiere text | KPresenter Template File | KOffice | Open Source |
| .KRA | Open Source | Fișiere grafice | Krita Image | Krita | Open Source |
| .KRF | SPARTA, Inc. | Fişiere de date | DNSSEC-Tools Keyrec Data File | KMESS (Kevin's Mesh Efficiency Simulator Software) | Open Source |
| .KS | Debian | Fişiere de sistem | Kickstart File | KeyStore Explorer | Open Source |
| .KSG | Open Source | Fişiere de imagini 3D | Kwalitan Segment File | Kwalitan | Open Source |
| .KSH | AT&T Labs | Fişiere executabile | Unix Korn Shell Script | AbiWord | Open Source |
| .KSM | Pfaff | Fişiere de date | Pfaff Embroidery Design File Format | Embroidermodder 2 | Open Source |
| .KTE | Open Source | Fişiere de date | Kite Design File | FoilMaker | Open Source |
| .KTX | Open Source | Fişiere de date | Kwalitan Data File | Kwalitan | Open Source |
| .KU | Open Source | Fişiere de date | Knowledge Explorer Knowledge Representation Knowledge Unit | my Knowledge Explorer | Open Source |
| .KVA | Open Source | Fişiere comprimate | KVIrc Compressed Archive | KVIrc | Open Source |
| .KVC | Open Source | Fişiere de date | KVC | KVIrc | Open Source |
| .KVS | Open Source | Fişiere de programator | KVIrc Script | KVIrc | Open Source |
| .KVT | Open Source | Fişiere de setări | KVIrc Heme | KVIrc | Open Source |
| .KWB | Open Source | Fişiere de date | Kwalitan Work File | Kwalitan | Open Source |
| .KWD | KDE | Fişiere text | KWord Document | KOffice | Open Source |
| .KWT | Open Source | Fişiere de setări | KVIrc Theme | KVIrc | Open Source |
| .L | Johan Bontes | Fişiere de date | Game Of Life File | ModPlug Player | Open Source |
| .LA | Open Source | Fişiere audio | Lossless Audio File | XMMS | Open Source |
| .LAB | Corel | Fişiere de aranjare în pagină | WordPerfect Label Definition File | BibExcel | Open Source |
| .LAP | Don Ho | Fișiere neobișnuite | Scheme Source Code | PSPad | Open Source |
| .LAY | Tecplot, Inc | Fişiere de date | Tecplot Layout File | MAME | Open Source |
| .LAZ | Global Heavy Industries | Fişiere de date | LiquidApps Project File | LASzip | Open Source |
| .LDF | Microsoft Corporation | Fişiere de date | SQL Server Transaction Log File | gVim | Open Source |
| .LDS | GNU Project | Fişiere de programator | Binutils LD Linker Script | gVim | Open Source |
| .LGL | Open Source | Fişiere de jocuri | LeechGet Download List | LeechGet | Open Source |
| .LINUX | Open Source | Fişiere de date | Linux Data File | Linux | Open Source |
| .LIS | SourceForge | Fişiere text | SQR (Structured Query Reporting) Output File | Notepad2 | Open Source |
| .LIST | Open Source | Fişiere de date | APT List File | Advanced Package Tool (APT) | Open Source |
| .LIT | Microsoft Corporation | Fișere eBook | Microsoft Reader eBook File | Calibre | Open Source |
| .LMH | Open Source | Fişiere de date | Memory Hacking Software Memory File | Memory Hacking Software | Open Source |
| .LMP | id Software | Fişiere de jocuri | Quake Engine Lump File | Nazi Zombies Portable | Open Source |
| .LNF | Open Source | Fişiere de date | Oyoaha Lookandfeel Interface Elements File | oyoaha lookandfeel | Open Source |
| .LNG | Nullsoft | Fişiere plugin | Winamp Language File | MAME | Open Source |
| .LNGX | Dominik Reichl | Fişiere de date | KeePaas Language Data | KeePass Password Safe | Open Source |
| .LNK | Microsoft Corporation | Fişiere de sistem | Windows File Shortcut | HxD | Open Source |
| .LNT | Gimpel Software | Fişiere de programator | PC-lint/FlexeLint Configuration File | MacVim | Open Source |
| .LNX | Commodore International | Fişiere comprimate | Commodore 64 Lynx Archive | VICE | Open Source |
| .LOF | Open Source | Fişiere audio | Audacity File List | Audacity | Open Source |
| .LOL | Apple | Fişiere de programator | LOLCODE Source Code FIle | AbiWord | Open Source |
| .LPI | Unknown Developer | Fişiere de date | Laser Printer Information | Lazarus IDE | Open Source |
| .LPK | ESRI | Fişiere GIS | ArcGIS Layer Package | Lazarus IDE | Open Source |
| .LPS | DAZ 3D | Fişiere de imagini 3D | Bryce Leaf Shape File | Lazarus IDE | Open Source |
| .LPT | Interscape | Fişiere de date | LogPlot Compiled Boring Log File | TOPS-10 | Open Source |
| .LQF | Open Source | Fişiere de date | LeechFTP Saved Queue | LeechFTP | Open Source |
| .LRC | Various Developers | Fișiere neobișnuite | Lyrics File | StepMania | Open Source |
| .LRF | Aequus Gaming LTD | Fişiere de jocuri | League Of Legends Replay File | Calibre | Open Source |
| .LRS | Open Source | Fișere eBook | Librie Reader Source File | Calibre | Open Source |
| .LRT | Aequus Gaming LTD | Fişiere de jocuri | League Of Legends Replay File | YACC | Open Source |
| .LRV | Konica Minolta | Fişiere de date | Konica Minolta Data Management Software Stored File | Media Player Classic | Open Source |
| .LRX | Sony | Fișere eBook | Sony Portable Reader File | Calibre | Open Source |
| .LRZ | Open Source | Fişiere comprimate | Lrzip Compressed Archive | Lrzip | Open Source |
| .LSP | Open Source | Fişiere de programator | Lisp Program Source Code File | Clozure CL | Open Source |
| .LST | Unknown Developer | Fişiere text | Data List | AbiWord | Open Source |
| .LTT | Hewlett-Packard | Fişiere de date | HP Library And Tape Tools Log | PSPad | Open Source |
| .LTX | GSC Game World | Fişiere de jocuri | S.T.A.L.K.E.R. Properties File | TEXnicCenter | Open Source |
| .LUG | Unknown Developer | Fişiere de jocuri | Game Data | Dragon UnPACKer | Open Source |
| .LVT | Open Source | Fişiere de setări | Land Surface Verification Toolkit Configuration | Land Information System Verification Toolkit (LVT) | Open Source |
| .LVZ | Open Source | Fişiere de jocuri | Continuum Zone Data Graphics | Subspace Continuum | Open Source |
| .LXK | Open Source | Fişiere de date | Lexicon Link-up File | COREX | Open Source |
| .LYT | Adminsoft | Fişiere de date | Adminsoft Document Layout File | AbiWord | Open Source |
| .LYX | Open Source | Fişiere de date | XWE File | XWE | Open Source |
| .LZM | Open Source | Fişiere comprimate | Slax Module | Slax | Open Source |
| .LZMA | Igor Pavlov | Fişiere comprimate | LZMA Compressed File | PeaZip | Open Source |
| .LZO | Open Source | Fişiere comprimate | LZO Compressed File | lzop | Open Source |
| .LZS | Open Source | Fişiere comprimate | LARC Compressed File Archive | ZipZag | Open Source |
| .LZX | Open Source | Fişiere comprimate | Amiga LZX Compressed File | cabextract | Open Source |
| .M | MathWorks | Fişiere de programator | MATLAB Source Code File | gVim | Open Source |
| .M15 | Moving Picture Experts Group | Fişiere video | MPEG Video File | CocoModX | Open Source |
| .M1A | Open Source | Fişiere audio | MPEG-1 Audio File | Media Player Classic | Open Source |
| .M1V | Roxio | Fişiere video | MPEG-1 Video File | Eltima Elmedia Player | Open Source |
| .M2A | Unknown Developer | Fişiere video | MPEG-1 Layer 2 Audio File | Media Player Classic | Open Source |
| .M2P | Moving Picture Experts Group | Fişiere video | MPEG-2 Program Stream File | Media Player Classic | Open Source |
| .M2T | Roxio | Fişiere video | HDV Video File | Squared 5 MPEG Streamclip | Open Source |
| .M3 | Blizzard Entertainment Inc. | Fişiere de imagini 3D | Blizzard MDX3 Model File | m3_Viewer | Open Source |
din 17 
