File extension index
Browse our index of file extensions and find guides for opening each type.
Over 852 extensions indexed.
Categories
Three-dimensional scene, mesh, and asset exchange formats used in modeling, visualization, and AR.
Most common extensions in this category.
- .stl
STL (Stereolithography) 3D Mesh
STL is a widely used 3D model exchange format for 3D printing and rapid prototyping, storing a surface as a triangle mesh. It commonly comes in either ASCII or binary form.
- .fbx
Autodesk FBX (Filmbox) 3D interchange format
.fbx is a proprietary 3D scene and asset exchange format owned by Autodesk and widely used to move models, animation, and scene data between 3D tools and game/animation pipelines.
- .obj
Wavefront OBJ (3D geometry) file
OBJ is a widely used text-based 3D geometry format that stores vertices, texture coordinates, normals, and polygon faces. It is commonly accompanied by a separate MTL material library file for appearance settings.
- .gltf
glTF (GL Transmission Format) 3D Asset
.gltf is a JSON-based 3D scene/model format (glTF 2.0) used to exchange and render 3D assets. It’s commonly opened in 3D tools like Blender, web apps via Three.js, and viewers that support glTF.
- .glb
glTF Binary (GLB)
.glb is the binary form of glTF 2.0, commonly used to deliver 3D models and scenes as a single file. It’s widely supported by 3D tools and viewers that can import/export glTF.
Archives
Open category pageCompressed and packaged files used for transfer, backup, and software distribution.
Most common extensions in this category.
- .zip
ZIP Archive
ZIP archives are widely used to compress and bundle multiple files or folders for easier storage and sharing.
- .rar
RAR Archive
.rar files are compressed archive containers used to bundle and compress one or more files, often including split (multi-part) archives. They’re commonly opened by WinRAR and can usually be extracted by tools like 7-Zip and The Unarchiver.
- .bz2
bzip2 Compressed File
.bz2 is a bzip2-compressed file, typically used to shrink a single file for storage or download. To use the contents, you usually decompress it with an extractor such as 7-Zip or the bzip2 command-line tool.
- .7z
7-Zip Archive
A .7z file is a 7-Zip compressed archive, commonly used to bundle and compress files with high compression ratios. Open it with 7-Zip on Windows or compatible archive tools such as WinRAR, Keka, The Unarchiver, p7zip, ZArchiver, or RAR.
- .gz
Gzip Compressed File
GZ files are compressed using the gzip algorithm, commonly used for reducing file size and bundling files with TAR.
Audio
Open category pageCommon music and sound formats for streaming, editing, and distribution.
Most common extensions in this category.
- .mp3
MPEG Audio Layer III
MP3 is a popular audio format known for its efficient compression, making it ideal for music and podcasts.
- .wav
Waveform Audio File
WAV files are high-quality audio files often used in professional audio recording and editing due to their lossless nature.
- .alac
Apple Lossless Audio Codec
ALAC files are audio files encoded using the Apple Lossless Audio Codec, providing high-quality audio compression without data loss.
- .aax
Audible Enhanced Audiobook
.aax files are audio files used by Audible for audiobooks, featuring enhanced features like images and links.
- .caf
Core Audio Format
CAF is an audio file format developed by Apple, used for storing audio data and supporting a wide range of audio formats.
Computer-aided design and technical drawing formats used in engineering, architecture, and manufacturing.
Most common extensions in this category.
- .stp
STEP (ISO 10303) Part 21 CAD exchange file
.stp is a STEP (ISO 10303) 3D CAD exchange file, typically a STEP physical file per ISO 10303-21 (Part 21). It’s commonly used to transfer 3D product geometry between CAD systems.
- .step
STEP (ISO 10303-21) CAD exchange file
.step is a widely used neutral CAD exchange format for sharing 3D product model data between different CAD systems. You typically open it by importing it into a CAD program such as Autodesk Fusion.
- .ifc
Industry Foundation Classes (IFC) BIM exchange file
.ifc is an open Building Information Modeling (BIM) exchange format used to share building and infrastructure models between different design, construction, and facility-management applications.
- .cdr
CDR CAD drawing
.CDR is the native drawing document format for CorelDRAW, commonly used for vector graphics, page layout, and print workflows. The most reliable way to open it is with CorelDRAW on a desktop computer.
- .cgm
CGM CAD drawing
.CGM (Computer Graphics Metafile) is an ISO/IEC 8632 standard graphics metafile that can store 2D vector graphics, raster graphics, and text. It is commonly used for technical illustrations and interchange between systems that support CGM.
Certificates
Open category pageDigital certificate and cryptographic trust files used for identity, signing, and secure connections.
Most common extensions in this category.
- .pfx
Personal Information Exchange (PFX)
.pfx is a PKCS #12 (PFX) container used to bundle certificates and (often) the associated private key into a single, typically password-protected file for import/export between systems.
- .pem
PEM-encoded Certificate
.pem is a text-based container format commonly used to store X.509 certificates, certificate chains, and sometimes private keys in Base64 with BEGIN/END markers. It is widely used by TLS software such as OpenSSL and Apache HTTP Server.
- .p12
PKCS#12 Certificate Bundle
.p12 is a PKCS #12 (also called PFX) container used to bundle an X.509 certificate chain together with its corresponding private key, typically protected by a password. It’s commonly opened/imported by certificate/key management tools such as Apple Keychain Access and OpenSSL.
- .csr
PKCS #10 Certificate Signing Request
.csr files are certificate signing requests used to obtain an X.509 certificate from a certificate authority (CA). They commonly contain a PKCS #10 request encoded as PEM (text) or DER (binary) and can be inspected or generated with OpenSSL.
- .der
DER-encoded X.509 Certificate
.der files most commonly contain binary DER-encoded ASN.1 data, especially X.509 certificates. They are typically opened for inspection or conversion using certificate tools such as OpenSSL.
Source code and script files used for software development and automation workflows.
Most common extensions in this category.
- .php
PHP script (PHP source code)
.php files typically contain PHP source code used on web servers to generate dynamic web pages and API responses. You can open them in a code editor, but they are usually executed by a web server (often via PHP-FPM) rather than “run” like a normal desktop app.
- .sql
SQL script (Structured Query Language)
.sql files contain SQL statements (queries, schema definitions, and data changes) that can be run by a database tool or opened as plain text for review and editing.
- .cs
C# source code file
.cs files contain C# source code used to build .NET applications and libraries. They are plain-text files typically edited in code editors and IDEs such as Visual Studio Code with C# tooling.
- .go
Go source file
.go files contain source code written in the Go (Golang) programming language. You can open them in code editors (for reading/editing) or build/run them with the Go toolchain.
- .tsx
TypeScript JSX (TSX) source file
.tsx is a TypeScript source code file that contains JSX syntax, commonly used with React-style UI components. You open it in a code editor (for viewing/editing) and build it with TypeScript tooling (for running in apps).
Configuration
Open category pageDeclarative configuration and schema files used to tune applications, builds, and runtimes.
Most common extensions in this category.
- .env
Dotenv environment variables file
.env is a plain-text configuration file commonly used to store environment variables as key=value pairs for local development and deployment tools.
- .ini
INI configuration file
An INI file is a plain-text configuration file format commonly used to store settings as sections and key/value pairs. You can open it in any text editor, and many apps (especially on Windows) read it as an initialization/config file.
- .toml
TOML configuration file
A .toml file is a human-readable configuration file written in TOML (Tom's Obvious, Minimal Language). It’s commonly used by developer tools (for example, Rust’s Cargo.toml and Python’s pyproject.toml) and can be opened with any text editor.
- .dtd
XML document type definition (.DTD)
.dtd files are Document Type Definition files used with XML (and related SGML-family) documents to define the allowed structure, elements, and entities. You typically open them in a text editor or an XML-aware editor/IDE.
Structured machine-readable files used by apps, APIs, and automation workflows.
Most common extensions in this category.
- .json
JSON data
.json files store structured data as plain text using the JSON (JavaScript Object Notation) format. They’re commonly used for web APIs, app configuration, and data exchange, and can be opened with any text editor or JSON-aware tools.
- .db
SQLite 3 Database
.db is commonly used for SQLite 3 database files—single-file relational databases used by many apps. You can open them with SQLite tools and many database browsers.
- .yaml
YAML File
.yaml is a YAML document: a human-readable data serialization format commonly used for configuration files and data exchange. You can open it with a text editor, or with editor support such as the YAML extension for Visual Studio Code.
- .sqlite3
SQLite 3 database
.sqlite3 is a SQLite version 3 database stored as a single cross-platform file. You can open it with SQLite’s sqlite3 command-line shell or any SQLite-capable database browser/library.
- .sqlite
SQLite 3 Database File
.sqlite is a SQLite 3 database stored as a single file. You open it with SQLite tools (for example, the SQLite command-line shell) or any application that supports SQLite.
Documents
Open category pageText and office document formats used for reports, slides, and spreadsheets.
Most common extensions in this category.
- .pdf
Portable Document Format
PDF files maintain consistent formatting across devices and are widely used for documents that require a fixed layout, such as forms and reports.
- .docx
Microsoft Word Open XML Document
DOCX files are widely used word-processing documents created by Microsoft Word, supporting rich text and multimedia elements.
- .xlsx
Microsoft Excel Open XML Spreadsheet
XLSX files are widely-used spreadsheet files that store data, formulas, and charts, and are compatible with various spreadsheet applications.
- .log
Plain-text Log File
.log files are typically plain-text logs that record events, messages, and errors from software or operating systems. They can usually be opened with basic text editors on any platform.
- .pptx
Microsoft PowerPoint Open XML Presentation
PPTX files are widely used for creating and sharing presentation decks with multimedia content.
eBooks
Open category pageDigital book formats used by e-readers, publishing tools, and reading apps.
Most common extensions in this category.
- .azw
Amazon Kindle eBook (AZW)
.azw is an Amazon Kindle eBook format used by Kindle devices and Kindle apps. It is part of the Kindle format family and is closely related to MOBI-based Kindle books.
- .mobi
Mobipocket eBook
.mobi is a Mobipocket eBook file used for distributing and reading ebooks, closely associated with Kindle-era ebook workflows. It can be opened in common ebook apps such as Kindle apps and Calibre.
- .kfx
Amazon Kindle KFX (Kindle Format 10) eBook
.kfx is a Kindle eBook format (Kindle Format 10) used for Kindle Store content and modern Kindle rendering features. It is typically opened on Kindle devices/apps, and is also used in Kindle publishing/preview workflows.
- .azw3
AZW3 ebook
.AZW3 files are eBook files primarily used by Amazon Kindle devices and apps, offering advanced formatting options.
- .fb2
FictionBook 2.0 (FB2) eBook
.fb2 is a FictionBook 2.0 eBook file stored as XML, commonly used for fiction and rich book metadata. You can read it in eBook apps that support FB2 or convert it to EPUB/MOBI using desktop tools like Calibre.
Fonts
Open category pageFont and glyph container formats used by typography, design, and publishing workflows.
Most common extensions in this category.
- .ttf
TrueType Font
.ttf is a TrueType font file used to install and use fonts in operating systems and applications. It may also be an OpenType font that uses TrueType outlines but is still stored with the .ttf extension.
- .otf
OpenType Font
.otf is an OpenType font file used by operating systems and applications to render text. You typically open it by installing the font or by viewing it in a font manager/editor.
- .woff2
WOFF2 Web Font
.woff2 is a WOFF2 (Web Open Font Format 2.0) file used to deliver compressed font data on the web. It’s most commonly “opened” by web browsers via CSS rather than installed like a desktop font.
- .woff
Web Open Font Format (WOFF)
.woff is a web font container format used by websites to deliver fonts efficiently to browsers. You typically “open” it by using it in CSS on a web page, or by inspecting/previewing it with font tools.
- .gf
GF data
.gf files are TeX/METAFONT “generic font” bitmap output files, typically converted to .pk for use by DVI/TeX tools. You usually open them with TeX utilities like gftype or convert them with gftopk.
Geospatial and gridded scientific datasets used in mapping, GIS, and environmental analysis.
Most common extensions in this category.
- .geojson
GeoJSON (RFC 7946) geospatial data
.geojson is a JSON-based format for exchanging geographic features (points, lines, polygons) and their properties. It is widely used in GIS and web mapping tools and follows the GeoJSON standard (RFC 7946).
- .shp
Esri Shapefile (geometry file)
.shp is the main geometry file in an Esri Shapefile dataset used to store vector GIS features. You typically open it in GIS software (for example ArcGIS Pro) together with its companion files such as .dbf and .shx.
- .kml
Keyhole Markup Language (KML)
KML is an XML-based GIS format for showing geographic features (placemarks, paths, polygons, overlays) on maps and virtual globes. It’s commonly opened in Google Earth and is also supported by GIS tools such as ArcGIS.
- .gpkg
OGC GeoPackage (SQLite) geospatial database
.gpkg is an OGC GeoPackage: a SQLite 3 database file with a standardized schema for geospatial data. It commonly stores vector layers and can also store raster/tiles in the same single file.
- .osm
OpenStreetMap OSM XML (map data)
.osm is an OpenStreetMap dataset stored as OSM XML, containing map features like nodes, ways, and relations. It’s commonly opened or imported into GIS tools such as QGIS, GDAL-based software, or data-integration tools like FME.
Images
Open category pageRaster and vector image formats used for photos, graphics, and design.
Most common extensions in this category.
- .jpg
JPEG Image
JPEG is a widely used image format known for its lossy compression, making it ideal for digital photography and web graphics.
- .png
Portable Network Graphics
PNG is a widely-used lossless image format known for its support of transparency and high-quality text rendering.
- .gif
Graphics Interchange Format
GIF is a widely used image format known for its ability to support animations and limited color palettes.
- .svg
SVG vector image
SVG files are XML-based vector graphics that maintain quality at any size, commonly used for web graphics.
- .heic
High Efficiency Image Container
HEIC files offer high-quality images with reduced file sizes, commonly used by modern smartphones like iPhones.
Machine learning
Open category pageModel and training-artifact formats used in machine learning and data science workflows.
Most common extensions in this category.
- .safetensors
SafeTensors tensor checkpoint format
.safetensors stores machine-learning tensor weights in a simple binary container with a small JSON header and raw tensor bytes. It is commonly used for sharing and loading model checkpoints (especially in the Hugging Face ecosystem) with an emphasis on safer, validation-friendly loading.
- .onnx
ONNX (Open Neural Network Exchange) model
.onnx is a serialized machine-learning model file in the Open Neural Network Exchange (ONNX) format, used to move models between tools and run inference in different environments. It’s commonly loaded by ONNX Runtime and other ONNX-capable ML software rather than “opened” like a document.
- .gguf
GGUF (GGML Universal Format) model file
.gguf is a binary file format used to store machine-learning models (tensors plus metadata), commonly for running LLMs with GGUF-capable local tools and runtimes (llama.cpp is a well-known example). It is designed for fast saving/loading and is often used to distribute quantized models for inference.
- .ml20
Machine Learning Model Format 2020
.ml20 files are used for storing machine learning models, typically created by specific machine learning frameworks.
Other
Open category pageMiscellaneous extensions that may map to multiple workflows or need sender context to identify.
Most common extensions in this category.
- .cdg
Compact Disc Graphics
CDG files are used to store graphics data for karaoke applications, often accompanying audio tracks.
- .sdp
Session Description Protocol
SDP files are used to describe multimedia communication sessions for streaming media.
- .ia
Internet Archive Format
The .ia file format is used by the Internet Archive for storing metadata and other related data.
- .mkm
Multimedia Knowledge Management File
MKM files are used for multimedia knowledge management, often in specialized software environments.
Subtitles
Open category pageCaption and subtitle text formats that accompany video and multimedia playback.
Most common extensions in this category.
- .ass
Advanced SubStation Alpha subtitles (.ASS)
.ASS files are most commonly Advanced SubStation Alpha subtitle files, not audio files. They are text-based subtitles used for styled captions, karaoke effects, positioning, and other advanced subtitle layout features.
- .srt
SubRip subtitles
.SRT is a SubRip subtitle file: a plain-text format that stores timed captions for video. You typically open it with a video player (as subtitles) or a text/subtitle editor (to view and edit the timings).
- .vtt
WebVTT subtitles
.VTT files are used for captions and subtitle tracks for media playback. Open with media players, subtitle editors, or video authoring tools. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: text/vtt.
System
Open category pageInstaller, executable, and system-level package formats used by operating systems and applications.
Most common extensions in this category.
- .aab
Android App Bundle
.aab is the Android App Bundle publishing format used to upload Android apps to Google Play. End users typically don’t “open” it like an APK; developers use Android Studio/Gradle and bundletool to build and test installable APKs from it.
- .apk
APK Archive File
An .apk file is an Android Package file used to distribute and install Android apps. It is a ZIP/JAR-based archive that can be installed on Android or inspected on desktop with Android development tools.
- .cab
CAB Archive File
.CAB is Microsoft’s Cabinet archive format used to bundle and compress one or more files, commonly in Windows installers and system components. On Windows you can often extract it with built-in tools like EXPAND, while other platforms usually require third-party archive utilities or transferring to a Windows PC.
- .deb
DEB Archive File
.deb is a Debian binary package archive used to install software on Debian-based Linux distributions. It is best opened, inspected, or installed using Debian package tools such as dpkg/dpkg-deb.
- .dmg
DMG Archive File
.dmg is an Apple Disk Image file most commonly used on macOS to distribute apps and other software in a mountable “virtual disk” container.
Video
Open category pageVideo container formats for playback, editing, and sharing.
Most common extensions in this category.
- .mp4
MPEG-4 Part 14 Video
MP4 is a popular multimedia container format used for storing video, audio, subtitles, and metadata, ideal for streaming and sharing across devices.
- .mkv
Matroska Video
MKV is a versatile multimedia container format known for supporting high-quality video and multiple audio and subtitle tracks.
- .3gp
3rd Generation Partnership Project Multimedia File
3GP is a multimedia container format primarily used for 3G mobile phones, but also playable on some 2G and 4G phones.
- .3gpp
3rd Generation Partnership Project Multimedia File
3GPP files are multimedia files used primarily for video and audio streaming on mobile networks.
- .mts
MPEG Transport Stream
MTS files are video files saved in the Advanced Video Codec High Definition (AVCHD) format, commonly used by Sony and Panasonic camcorders.
Web markup, stylesheet, and related assets used by browsers and web platforms.
Most common extensions in this category.
- .jsx
JSX (JavaScript XML) source file
.jsx is JavaScript source code that includes JSX, an XML-like syntax commonly used to write React UI components. You open it in a code editor (for viewing/editing) and typically compile it to plain JavaScript with tools like Babel or TypeScript.
- .war
Web Application Archive (WAR)
.war is a Web Application Archive used to package Java/Jakarta servlet-based web applications for deployment on a servlet container (for example, Apache Tomcat or Jetty). It is a ZIP-based Java archive that contains application classes, libraries, and web resources in a standard layout.
- .wasm
WebAssembly binary module
.wasm is the binary module format for WebAssembly, designed to run fast and efficiently in web browsers and other runtimes. You typically “open” it by loading it in a WebAssembly runtime (often via JavaScript in a browser) or by running it with a standalone runtime such as Wasmtime.
- .css
CSS stylesheet
.css is a Cascading Style Sheets (CSS) text file used to control the look and layout of web pages. You can open it in any text editor, and it is commonly edited with code editors that understand CSS.
- .mht
MHTML (Web Archive) file
.mht is an MHTML web archive that saves a complete web page (HTML plus images/CSS and other referenced files) into a single file. It’s commonly opened in modern web browsers such as Google Chrome and Microsoft Edge.