File extension facts for kids

A file extension is a short ending at the very end of a filename. It's like a special code that tells your computer what type of file it is. This helps your computer know which program should open the file. For example, if you see a file named report.TXT, the ".TXT" part is the file extension. It tells your computer that this is a plain text file, and it can be opened by a simple text editor program. Most file extensions are three or four letters long and come after a dot in the file's name.

Common File Extensions and What They Do

Here are some common file extensions you might see and what they mean:

Document and Text Files

• TXT files are plain text files. They usually contain simple words and numbers without any special formatting.
• ODT are Open Document text files, often used by free office programs.
• DOC or DOCX are text documents made with Microsoft Word.
• XLS or XLSX are spreadsheet documents, often created with Microsoft Excel. They are great for organizing numbers and data.
• PPT or PPTX are presentation files, like those made with Microsoft PowerPoint. They are used for slideshows.

Image Files

• BMP are bitmap picture files. These are often larger image files.
• JPG or JPEG are picture files in the JPEG format. These are very common for photos because they can be made smaller.
• PNG are image files that can have transparent backgrounds.
• GIF are image files that can also be short, moving animations.

Audio Files

• MP3 are music files in the MP3 format. These are very popular for songs and audio.
• AAC are Advanced Audio Coding music files, often used for music on Apple devices.
• FLAC are Free Lossless Audio Codec files. They keep the original sound quality without losing any details.
• ALAC are Apple Lossless Audio Codec files, similar to FLAC but for Apple devices.
• WMA are Windows Media Audio sound files, often used on Windows computers.

Video Files

• MPEG are motion picture encoded video files.
• MKV are Matroska Video Codec files. They can hold many different types of video and audio.
• WMV are Windows Media Video files, often used on Windows computers.
• MP4 are common video files that can also hold audio and images.

Web and Program Files

• HTM or HTML are Hyper Text Markup Language files. These are the building blocks of most web pages you see online.
• PHP are web server scripts. These files help create dynamic web pages that change based on what you do.
• EXE are Microsoft Windows executable program files. These are programs that you can run on your computer.
• DLL are Dynamic Link Libraries. These are special files that programs use to share code and resources on Windows.
• JAR are Java archive files. These are used for programs written in the Java language.
• SH are Unix / Linux shell script files. These are small programs that automate tasks on Linux or Unix computers.

Compressed Files

• ZIP are Compressed files. They use a special method to make files smaller, which is great for sending many files at once.
• Z are Unix / Linux compressed files.
• BZ2 are bzip2 block compressed files. These offer very good compression, making files much smaller.
• TAR are Unix / Linux tape archive files. These combine many files into one, often before compressing them.

How Computers Use File Extensions

Your computer uses file extensions to understand what kind of data is in a file. When you double-click a file, your computer looks at its extension. Then, it knows which program to open the file with. For example, if you click a ".JPG" file, your computer will likely open it with an image viewer. If you click a ".MP3" file, it will open with a music player.

You can often change the default program your computer uses for a certain file extension. This means you can tell your computer to open all ".TXT" files with a different text editor if you prefer.

See also

In Spanish: Extensión de archivo para niños