File extension index
Browse our index of file extensions and find guides for opening each type.
Over 754 extensions indexed.
Categories
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 is a compressed archive format known for strong compression and multi-part archives.
- .bz2
Bzip2 Compressed File
BZ2 files are compressed archive files created using the Bzip2 compression algorithm, commonly used for reducing file sizes.
- .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.
- .cdr
CDR Image File
.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 Image File
.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.
- .dwg
DWG Image File
.DWG is a CAD drawing format best known as AutoCAD’s native drawing file, used for 2D/3D design and technical documentation. Open it with Autodesk AutoCAD or a DWG viewer such as Autodesk DWG TrueView.
- .dxf
DXF Image File
.DXF is Autodesk’s Drawing eXchange Format, widely used to exchange 2D/3D CAD drawings between different applications. It’s commonly opened and edited in CAD programs such as AutoCAD-compatible tools and LibreCAD.
Certificates
Open category pageDigital certificate and cryptographic trust files used for identity, signing, and secure connections.
Most common extensions in this category.
- .cer
CER Data File
.CER is most commonly an X.509 digital certificate file used to identify a website, person, device, or organization. It typically contains a public certificate (not a private key) and can be viewed/installed with built-in tools on major desktop operating systems.
- .crl
CRL Data File
.CRL is a Certificate Revocation List file used in X.509 PKI to publish certificates that have been revoked. It’s typically opened with certificate tools (Windows Certificate Import Wizard) or inspected/converted with OpenSSL.
- .crt
CRT Data File
.CRT most commonly contains an X.509 digital certificate (often PEM or DER encoded) used for TLS/SSL and trust chains. You typically open it with certificate tools (view/import) rather than “run” it like a document.
Source code and script files used for software development and automation workflows.
Most common extensions in this category.
- .cc
CC Document File
.cc most commonly refers to a C++ source code file. You open it in a code editor or IDE, and you can compile it with a C++ compiler such as GCC (g++).
- .hh
HH Document File
.hh is most commonly a C++ header source file used to declare interfaces (functions, classes, constants) for C++ programs. You open it with a text editor or an IDE, not a document viewer.
- .js
JS Document File
.JS files are used for software development, scripts, and automation tasks. Open with source-code editors or IDEs that support syntax highlighting and tooling. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: text/javascript.
- .pl
PL Document File
.PL files are used for software development, scripts, and automation tasks. Open with source-code editors or IDEs that support syntax highlighting and tooling. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: text/x-perl.
- .py
PY Document File
.PY files are used for software development, scripts, and automation tasks. Open with source-code editors or IDEs that support syntax highlighting and tooling. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: text/x-python.
Structured machine-readable files used by apps, APIs, and automation workflows.
Most common extensions in this category.
- .json
JavaScript Object Notation
JSON is a lightweight text format used for APIs, configuration files, and data exchange.
- .pkpass
Apple Wallet Pass
PKPASS files contain digital tickets, boarding passes, coupons, and loyalty cards for wallet apps.
- .dat
Data File
.dat files are generic data files that can contain various types of data, often used by specific applications.
- .ac
AC Data File
.AC files are specialized data files used in specific software environments, often requiring niche applications to access them.
- .cl
CL Data File
.CL most commonly refers to an XML “Simple-Filter” document used with SIP event notification filtering. It is essentially an XML file (media type: application/simple-filter+xml) that is often best opened with an XML-capable editor or viewer.
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.
- .pptx
Microsoft PowerPoint Open XML Presentation
PPTX files are widely used for creating and sharing presentation decks with multimedia content.
- .txt
Plain Text File
TXT files contain plain text and can be opened on any operating system with a variety of text editors.
eBooks
Open category pageDigital book formats used by e-readers, publishing tools, and reading apps.
Most common extensions in this category.
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
Scalable Vector Graphics
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.
Other
Open category pageBrowse Other extensions and troubleshooting guides.
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
ASS Audio File
.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
SRT Document File
.SRT 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/plain.
- .vtt
VTT Document File
.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.
- .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.
- .iso
ISO Archive File
.ISO files are used for installation packages, updates, and system-level deployment workflows. Open only with trusted system utilities or package managers. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: application/x-iso9660-image.
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.
- .css
CSS Document File
.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.
- .htm
HTM Document File
.HTM files are used for web pages, browser rendering, and front-end assets. Open with web browsers, code editors, or build tools for web development. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: text/html.
- .svgz
SVGZ Image File
.SVGZ files are used for web pages, browser rendering, and front-end assets. Open with web browsers, code editors, or build tools for web development. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: image/svg+xml.
- .xml
XML Document File
.XML files are used for web pages, browser rendering, and front-end assets. Open with web browsers, code editors, or build tools for web development. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: application/xml.
- .xul
XUL Document File
.XUL files are used for web pages, browser rendering, and front-end assets. Open with web browsers, code editors, or build tools for web development. This guide covers opening methods, troubleshooting, and security best practices. Common MIME type: text/xul.