| Extension | File Type | Files scanned | Contributor |
| J | JAR Compressed Archive (with Security Envelope) | 18 | |
| J | JAR compressed archive | 17 | |
| J2A | Jazz Jackrabbit 2 Animations library | 2 | |
| J2B | Jazz Jackrabbit 2 Music data | 24 | |
| J2B | Jazz Jackrabbit 2 module | 2 | |
| J2D | Jazz Jackrabbit 2 library Data | 2 | |
| J2E | Jazz Jackrabbit 2 Episode | 7 | |
| J2K/CFG/INI | Joy2Key settings | 16 | |
| J2L | Jazz Jackrabbit 2 Level data | 48 | |
| J2M | Jazz Jackrabbit 2 Macro | 5 | |
| J2S | Jazz Jackrabbit 2 language Strings | 6 | |
| J2T | Jazz Jackrabbit 2 Tiles set | 26 | |
| J2V | Jazz Jackrabbit 2 Video | 9 | |
| J6I | Ricoh digital camera image | 2 | |
| JACKSUM | Jacksum fingerprints | 7 | Johann N. Loefflmann |
| JAD | Java Application Descriptor | 14 | |
| JAM | JAM bitmap | 2 | |
| JAM | JAM compressed volume | 8 | |
| JAM | JAM game video | 19 | |
| JAM | JamCracker module | 41 | |
| JAM | Lego Racers game data archive | 2 | |
| JAM | Zyclunt game data archive | 2 | |
| JAP | Nonogram puzzle | 26 | |
| JAP | jalbum Project | 40 | Scrapie |
| JAR | JARCS compressed archive | 4 | |
| JAR | Java Archive | 87 | |
| JAR | Minecraft Fabric Mod | 15 | |
| JAR | Mozilla Firebird theme | 17 | |
| JAR | QiC JAR ebook | 10 | |
| JARDESC | Eclipse JAR settings | 13 | |
| JAS | Cheetah3D format | 10 | |
| JAS | Cheetah3D format (binary) | 16 | |
| JB2/JBIG2 | JBIG2 bitmap | 2 | |
| JBA | Jabaco project | 18 | |
| JBB | Javelin Building Block | 6 | |
| JBEAM | BeamNG vehicle definition format | 8 | |
| JBF | PaintShop Pro Browser cache | 13 | Dr.Ryo(TM) |
| JBG/JBIG/BIE | JBIG raster bitmap | 31 | |
| JBI | Motoman Relative Job | 10 | |
| JC | JCALG1 compressed data | 2 | |
| JCA | JOC-CALC spreadsheet (v1.0) | 4 | |
| JCC | Japan Crossword File (Dmitry Torshin format) | 2 | .Cryorb |
| JCD | JewelCAD Design | 1282 | |
| JCE | JWPce document | 6 | |
| JCEKS | Java SunJCE KeyStore | 5 | |
| JCF | JTAG Chain File | 16 | |
| JCI | JTAG Chain Information | 12 | |
| JCL | JCL script (with rem) | 12 | |
| JCLIC | JClic project | 17 | |
| JCP | JCreator Project | 14 | |
| JCP | JWPce Project | 2 | |
| JCP | Jesusonic Preset | 9 | |
| JCW | JCreator Workspace (XML) | 3 | |
| JCW | JCreator Workspace (v1.0) | 5 | |
| JCW | JCross CrossWords puzzle | 12 | |
| JCW | Xara color palette | 3 | |
| JDB | Symantec Endpoint Protection Update | 14 | |
| JDBG | Embedded JCL debug info | 2 | |
| JDF | Jeol JDF format | 13 | |
| JDF | Job Definition Format Job File | 4 | |
| JDP | BlackBerry JDE Application Project | 14 | |
| JDT | Capture Classic Filler - Accelio JetForm | 10 | |
| JDX/DX/SMP | JCAMP-DX format | 58 | |
| JED | CUPL format | 24 | |
| JED | PALASM (var.1) | 2 | |
| JED | PALASM (var.2) | 5 | |
| JED | PALASM (var.3) | 4 | |
| JED | PALASM (var.4) | 2 | |
| JED | Xilinx JEDEC programming spec | 19 | |
| JEF | Janome NH10000 Sewing Machine Stitch | 7 | FILExt |
| JEM | JSON Entity Model | 28 | |
| JET | Bloons Tower Defense 5 Deluxe game data container | 4 | |
| JEX | JustSystems Executable | 38 | |
| JFC | Java Flight Recorder event settings | 42 | |
| JFD | JFD Disk Image (unzipped) | 8 | |
| JG6 | BigJig Jigsaw | 4 | |
| JGCSCS | EditPad Pro Custom Syntax Coloring Scheme (ASCII) | 9 | |
| JGCSCS | EditPad Pro Custom Syntax Coloring Scheme (UTF-8) | 6 | |
| JHM | JavaHelp map | 6 | |
| JHR | JAM message Header | 2 | |
| JIC | JTAG Indirect Configuration | 7 | |
| JIF | Jeff's Image Format bitmap | 24 | |
| JIG | GameHouse Jigsaw Game | 52 | |
| JIG | Jigsaw Puzzle | 13 | |
| JIGDO | Jigsaw Download (ungzipped) | 25 | |
| JIMG/JTEX | J Texture | 3 | |
| JKS/KEYSTORE | Java KeyStore | 5 | |
| JKS | Star Wars: Jedi Knight - Dark Forces II save game | 118 | | NEW! |
| JLS | JPEG-LS bitmap | 11 | |
| JMA | JMA compressed archive | 2 | |
| JMF | Janko Mrsic-Flogel module | 6 | |
| JMG | 16 bit adaptive RLE compressed bitmap | 2 | |
| JMP | JMP PRO data table (v10) | 24 | |
| JMP | JMP PRO data table (v11) | 41 | |
| JMP | JMP PRO data table (v12) | 39 | |
| JMP | JMP PRO data table (v13) | 153 | |
| JMP | JMP PRO data table (v14) | 120 | |
| JMP | JMP PRO data table (v15) | 35 | |
| JMP | JMP PRO data table (v16) | 11 | |
| JMP | JMP PRO data table (v17) | 3 | |
| JMP | JMP PRO data table (v9) | 17 | |
| JMP | JMP data table (alternate, generic) | 11 | |
| JMP | JMP data table (generic) | 287 | |
| JMP | JMP data table (v10) | 5 | |
| JMP | JMP data table (v11) | 4 | |
| JMP | JMP data table (v12) | 5 | |
| JMP | JMP data table (v13) | 5 | |
| JMP | JMP data table (v14) | 4 | |
| JMP | JMP data table (v15) | 6 | |
| JMP | JMP data table (v16) | 7 | |
| JMP | JMP data table (v17) | 8 | |
| JMP | JMP data table (v5) | 2 | |
| JMP | JMP data table (v9) | 4 | |
| JMX | Hot Potatoes JMix project | 19 | |
| JMX | JMeter XML test plan (v1.x) | 13 | |
| JN | Student Writing Center Journal | 2 | |
| JNB | Sigma Plot Workbook | 9 | |
| JNG | JPEG Network Graphics bitmap | 14 | |
| JNILIB | JNI Library | 19 | |
| JNLP | Java Web Start application descriptor | 20 | |
| JNT | Windows Journal | 22 | |
| JO | FlowJo Mac Workspace | 13 | |
| JOB | Compass and Ruler Job | 31 | |
| JOB | Labeler (v2.0) / Labels Unlimited (v1.0) Job | 19 | |
| JOB | Labeler (v3.0) / Labels Unlimited (v2.0) Job | 44 | |
| JOB | Pro Video Job | 2 | |
| JOB | Tripod Data Systems Job file | 2 | |
| JOBOPTIONS | Acrobat Distiller Job Options | 73 | |
| JOC | WITCH-DOS Job Control | 28 | |
| JOC | Ways Job Control | 9 | |
| JOURNAL/JOURNAL~ | systemd journal | 7 | |
| JOURNAL~ | systemd journal (empty) | 3 | Joerg Jenderek |
| JOY | EzDraw drawing | 2 | |
| JOY | Trackjoy GUS Tracker module | 2 | |
| JP2 | JPEG 2000 bitmap | 28 | |
| JP6 | Atlantis Evolution game data archive | 2 | |
| JPC/J2C/J2K | JPEG-2000 Code Stream bitmap | 28 | |
| JPEG | Frogwares Game Development Studio saved game (generic) | 86 | |
| JPEG | Journey to the Center of the Earth save game | 38 | |
| JPEG | Sherlock Holmes: Secret of the Silver Earring save game | 68 | |
| JPEGT | JPEG Transparent bitmap | 3 | |
| JPF/JPX | JPEG 2000 eXtended bitmap | 4 | |
| JPG/JPEG | DualPhoto JPEG bitmap | 3 | |
| JPG/JPEG | JFIF JPEG bitmap | 76 | |
| JPG/JPEG | JFIF-EXIF JPEG Bitmap | 12 | |
| JPG/JPEG | JPEG bitmap | 78 | |
| JPG/JPEG | Macintosh JPEG bitmap (MacBinary) | 4 | |
| JPG | Pegasus JPEG bitmap | 24 | |
| JPK | JAM Packer compressed disk image | 5 | |
| JPK | Jeepers Key/index | 4 | |
| JPM | JPEG 2000 Multi-layer bitmap | 4 | |
| JPM | Thunder compressed data (v2.00) | 4 | |
| JPO | Jason Page audio format (old) | 7 | |
| JPR | Jeepers Reference DB | 3 | |
| JPS | JPEG Stereoscopic bitmap | 28 | |
| JPS | Jolly Print Studio graphic | 9 | |
| JPX | JBuilder Project | 43 | |
| JPX | jalbum image info | 9 | |
| JQZ | JQuiz quiz | 15 | |
| JR2 | Fishing Simulator 2 addon | 5 | Mamo |
| JR2 | JR-200 Raw tape format | 3 | |
| JRC | JRchive compressed archive | 7 | |
| JRC | JRipCart PCjr cartridge image | 2 | |
| JRN | JMP Journal (with rem) | 16 | |
| JRPRINT | JasperReports Print | 26 | |
| JRSR | JPC-RR rerecording | 43 | |
| JRXML | JasperReports JRXML report definition | 18 | |
| JS | Mozilla (Netscape) settings | 4 | |
| JSA | JRun Server Application | 8 | |
| JSB | JavaScript Bean file | 11 | |
| JSC | Bytenode Compiled JavaScript | 15 | |
| JSC | Bytenode Compiled JavaScript (Electron) | 8 | |
| JSC | QML JavaScript cached | 26 | |
| JSC | V8 JavaScript Compiled code (generic) | 12 | |
| JSD | eFAX Jet Suite Document | 4 | |
| JSF | Jahshaka Scene File | 4 | |
| JSFL | JavaScript Flash Obfuscated | 2 | |
| JSMS | JSON MS/MS | 11 | |
| JSON | 3D Tiles | 17 | |
| JSON | BASIC8 program info | 7 | |
| JSON | Bambu Studio filament profile | 162 | |
| JSON | Bambu Studio machine profile | 20 | |
| JSON | Bambu Studio process profile | 42 | |
| JSON | C2PA manifest | 9 | |
| JSON | CSV Dialect Description Format | 5 | |
| JSON | Content Addressable Archive info/layout | 6 | |
| JSON | Coriolis.io ship loadout | 10 | |
| JSON | Croissant dataset description (0.8) | 17 | |
| JSON | Croissant dataset description (1.0) | 19 | |
| JSON | CryENGINE DBATable | 4 | |
| JSON | Cura extruder definition | 234 | |
| JSON | Cura quality settings | 1169 | |
| JSON | Cura theme | 4 | |
| JSON | Cyberpunk 2077 save game (add. data) | 40 | |
| JSON | DPaint JS bitmap | 6 | |
| JSON | DPaint JS palette | 6 | |
| JSON | DREAMM config | 6 | |
| JSON | Dexie IndexedDB export | 6 | |
| JSON | DroidPad custom layout | 5 | |
| JSON | EasyEDA source | 26 | |
| JSON | Firefox bookmark (JavaScript Object Notation) | 29 | Joerg Jenderek |
| JSON | Gyroflow camera preset | 2380 | |
| JSON | HTTP Archive | 7 | |
| JSON | HstWB Installer image info | 11 | |
| JSON | HstWB Installer package info | 19 | |
| JSON | JSON array (generic) | 7 | |
| JSON | JSON object (generic) | 320 | |
| JSON | JW Library manifest | 4 | |
| JSON | Karabiner-Elements configuration | 13 | |
| JSON | Live2D Cubism 3 model settings | 41 | |
| JSON | Live2D Cubism 3 motion data | 536 | |
| JSON | Live2D Cubism 3 physics data | 40 | |
| JSON | Live2D Cubism expression data | 94 | |
| JSON | Live2D Cubism model-settings data | 53 | |
| JSON | Live2D Cubism physics data | 72 | |
| JSON | Live2D Cubism pose data | 23 | |
| JSON | Lottie animation | 33 | |
| JSON | MAME plugin config | 13 | |
| JSON | MathOptFormat | 9 | |
| JSON | Node-RED flow | 7 | |
| JSON | Node.js Package Manifest | 9 | |
| JSON | Nuendo JSON template | 20 | |
| JSON | Open Brush 3D metadata | 48 | |
| JSON | Open3D PoseGraph | 10 | |
| JSON | QMK keyboard info | 6 | |
| JSON | QMK keymap | 17 | |
| JSON | QMK keymap (UTF-8) | 6 | |
| JSON | RO-Crate Metadata | 11 | |
| JSON | Scoop bucket | 2965 | |
| JSON | SofTest encrypted answers data | 10 | |
| JSON | Speakeasy configuration | 5 | |
| JSON | SpeedCrunch session | 6 | |
| JSON | Splits.io Exchange Format | 4 | |
| JSON | Timberborn map (unzipped) | 23 | |
| JSON | Trizbort.io map | 7 | |
| JSON | TypeScript compiler options | 4 | |
| JSON | VIA keypad definition | 10 | |
| JSON | Vega visualization | 938 | |
| JSON | VirusTotal graph | 9 | |
| JSON | Xcode Asset Catalog | 23 | |
| JSON | cool-retro-term profile | 7 | |
| JSON | opencomic syndication format | 4 | |
| JSON | radiobrowser stations info | 31 | |
| JSONG | Jacker Song | 4 | |
| JSONLZ4 | Mozilla JSON compressed bookmark | 36 | |
| JSONX | JSONx | 8 | |
| JSPF | JSON Playlist File | 9 | |
| JSPROJ | Visual Studio JavaScript Project | 12 | |
| JSRC | Jabaco Source | 38 | |
| JST | Jnes save state | 20 | |
| JSXBIN | Binary ExtendScript Script | 5 | |
| JT | Jupiter Tesselation 3D visualization format | 191 | |
| JTB | DSP Tracker Joined Module Bank | 2 | |
| JTD | Ichitaro document | 26 | |
| JUCER | JUCE project | 10 | |
| JUI | Qt Jambi User Interface | 21 | |
| JV | Bitmap Brothers JV video | 2 | |
| JVEROM | ParaJVE ROM | 4 | |
| JVX | JavaView JVX geometry | 6 | |
| JW/JWT | JustWrite document | 2 | |
| JWC | JewelCase Maker project | 6 | |
| JWC | Jw_cad data | 8 | |
| JWL | Easy CD Creator's Jewel case | 21 | |
| JWL | Easy CD Creator's label (v5) | 4 | |
| JWLIBRARY | JW Library backup | 4 | |
| JWP | Japanese Word Processor document | 2 | |
| JWPUB | JW Pubblication | 6 | |
| JWR | LegaSuite GUI Runtime | 6 | |
| JWS | JDeveloper Java Workspace Settings | 10 | |
| JXB/XJB | JAXB Bindings | 21 | |
| JXL | JPEG XL bitmap | 2 | |
| JXL | JPEG XL bitmap (ISOBMFF) | 6 | |
| JXR/WDP | JPEG XR bitmap (WMPHOTO) | 6 | Joerg Jenderek |
| JXS | JayTrax module | 28 | |
| JZLIB | Lemur Module | 5 | |
| JZML | Lemur Layout | 8 | |