File extensions
IONOS editorial team6 mins
Everyone has had the experience of encountering file extensions they did not know at some point or other. You might immediately recognise the common ones like JPG or MP3 and know that it is either an image file or a music file, respectively. However, in addition to these well-known filename extensions, there are countless others that users may not recognise. Naturally, it does not help that new file extensions are constantly being added to the pool of existing ones.
In the following article, we will provide a list of the most important file extensions for text, image, video, and various other digital files.
What is a file extension?
A file extension (also known as a filename extension, file type, or file suffix) is the last part of a file name. This element is separated from the actual file name by a dot and typically consists of three to four characters. The file extension can be used to identify the type of file format as well as which applications can be used to open and edit the file.
For example, a PDF file is a Portable Document Format file which can be opened with programs such as Adobe Reader. Since file extensions are not standardised, it is possible for one extension to be used for different file types. Some operating systems hide file extensions so that inexperienced users cannot accidentally modify them.
The most common file extensions in a list
In the following sections, we have provided tables summarising the most important extensions for various types of computer files such as images, text documents, videos, and system files.
File extensions for image files
| Extension | Description | Format |
| .bmp | BMP (also called bitmap) is a two-dimensional raster graphics format developed for Microsoft and IBM operating systems. | Graphics format |
| .gif | GIF (Graphics Interchange Format) is a special graphics format for images, animations, and short clips. | Graphics format |
| .heif, .heic | HEIF (High Efficiency Image Format File) is a container format that can combine any number of images in one file to save space. | Graphics format |
| .jpg, .jpeg | The JPEG format (Joint Photographic Experts Group) is one of the most common graphics formats. It has a comparatively small file size while maintaining high image quality. | Graphics format |
| .png | PNG stands for Portable Network Graphics and is a commonly used graphics format with lossless data compression. | Graphics format |
| .psd | PSD (Photoshop Document) is the standard format for files created with Adobe Photoshop. | Graphics format |
| .svg | The SVG file extension (Scalable Vector Graphics) identifies files with two-dimensional vector graphics. | Graphics format |
| .tif, .tiff | TIFF (or TIF) stands for Tagged Image File Format. This graphics format is considered the standard for storing high-resolution photos and print data. | Graphics format |
We go over the most important image formats in more detail in one of our feature articles.
File extensions for text files and other documents
| Extension | Description | Format |
| .doc, .docx | These are the two file extensions for Microsoft Word text documents. In addition to text, these files can also contain images and graphics. | Text file |
| .md | MD (Markdown Documentation) is a format for plain text documents without any additional elements. | Text file |
| .odt | The extension ODT (OpenDocument Text) identifies text documents created with the free-to-use office software suite Apache OpenOffice. | Text file |
| Adobe’s PDF file extension (Portable Document Format) is probably the most commonly used file format across the Internet. PDFs can contain text, images, graphics, videos, and audio. | Document format | |
| .ppt, .pptx | PPT and PPTX, which were introduced in 2007, are file extensions for editable files created in the popular Microsoft presentation program PowerPoint. | Presentation file |
| .rtf | RTF (Rich Text Format) is a file format that enables text to be shared between programs in different operating systems. | Text file |
| .txt | The TXT file extension identifies plain text documents that contain no formatting or images. | Text file |
| .xls, .xlsx | XLS and XLSX identify files created in the Microsoft spreadsheet program Excel. | Spreadsheet file |
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Audio files
| Extension | Description | Format |
| .flac | FLAC (Free Lossless Audio Codec) is a format for free lossless audio compression. | Audio file |
| .mp3 | MP3 (MPEG Audio Layer 3) is the best known and most widely used format for audio files. | Audio file |
| .aac | The audio file format AAC (Advanced Audio Coding) is designed to be the successor to the MP3 format. | Audio file |
| .ogg | OGG is a container format for multimedia files. | Container format |
| .wma | WMA (Windows Media Audio) is a compressed audio format. | Audio file |
| .wav, .wave | WAVE (Waveform Audio File Format) is a container format for the lossless storage of audio files. | Audio file |
Video files
| Extension | Description | Format |
| .avi | AVI (Audio Video Interleave) is a video container format created by Microsoft. | Video format |
| .flv | FLV (Flash Video) identifies an open container file format that is primarily used for sending video content over the Internet. | Video format |
| .mov | MOV is a file format developed for Apple’s QuickTime Player. | Video format |
| .mp4 | MP4 is a modern video format designed for MPEG-4 content. | Video format |
You can learn more about the most important video formats in our feature article.
System files
| Extension | Description | Format |
| .dll | The file extension DLL (Dynamic Link Library) identifies dynamic software libraries. | System file |
| .drv | DRV files (driver files) enable communication between computers and hardware devices. | Driver file |
| .ini | INI is a configuration file for initialising program settings. | Initialisation file |
| .tmp | The TMP file extension identifies automatically generated files that temporarily store data. | Temporary file |
Compressed data files
| Extension | Description | Format |
| .7z | 7z is a free file format for archiving files. | Archive file |
| .jar | JAR (Java Archive) is a zip file that has a library containing multiple files. | Archive file |
| .rar | A RAR file is a compressed file, or data container, that holds one or more files or folders. | Archive file |
| .zip | ZIP is probably the most popular file format for compressing files. | Archive file |
Executable files
| Extension | Description | Format |
| .bat | BAT (batch file) is a script file containing a series of executable commands. | Batch file |
| .com | The COM file extension (command) identifies executable programs in MS-DOS. | Executable file |
| .exe | The EXE file extension identifies executable applications in Windows-based systems. | Executable file |
File extensions for web file formats
| Extension | Description | Format |
| .css | CSS stands for Cascading Style Sheets and is used for website design. | Stylesheet language |
| .html | HTML (Hypertext Markup Language) is a text-based markup language. | Document format |
| .js | JavaScript is a scripting language for websites. | JavaScript code file |
| .php | PHP (Hypertext Preprocessor) is a scripting language for web applications, which is widely used around the world. | Script file |
| .xml | XML (Extensible Markup Language) is a text-based markup language. | Document format |
Email files
| Extension | Description | Format |
| .eml | EML is the file extension for text-based emails. | Email file |
| .msg | MSG is the file extension for emails in Microsoft Outlook. | Email file |
| .ost | An OST file is an offline Microsoft Outlook data file with locally stored data. | Data file |
| .pst | A PST file is a Microsoft Outlook data file containing personal information. | Container file |
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