An identification system added to the end of a file name, indicating the type of file or the program it is associated with.
When downloading content from the Web, you will undoubtedly encounter many different types of electronic file formats. The way to identify the file type is by looking at its extension, typically expressed as a dot followed by 2 to 4 letters (.xxx).
The file extension will tell you whether or not a file is compatible with your computer or if you need additional software in order to open the file or view its contents.
Also See: File Formats and Extensions
Frequently Asked Questions
I don’t see a file extension. How can I find what type of file this is?
Some operating systems allow you to hide file extensions, or do so by default. If you’re running Windows, you can update this setting from file explorer. On the view tab, check the “File name extensions” box. On a Mac, go to the desktop, then click the Finder menu and select Preferences. On the Advanced tab, check the “Show all file extensions” box. On mobile devices, you may need to install a file explorer app to view your individual files. Most of these will display file extensions by default. If not, you should be able to change the view in the app’s settings menu.
Why do files have extensions?
Most files are designed to be run by a specific program. Including a file extension allows your computer to quickly identify the required program and launch it when you request to open the file. If the computer does not recognize the file extension, it may prompt you with a list of programs it has determined are most likely to open the file. If you know the correct program, you can select it from that prompted list, or search your computer for it. If the file does not contain a file extension, your computer will have no way of associating that file with a specific program.
Can I change a file’s extension?
You can, but it is not recommended. Doing so will make your computer incapable of associating the correct program with the file, and could make the file unreadable. However, there are times when you may want to change the file extension. For instance, if you want to deliberately change the program associated with a specific file, but not change it for all files of that extension. To do so, you need to first turn on file extension view (see above), and then rename the file. You should be able to edit the extension just as you can the rest of the file name. If you do rename an extension, make sure to note its original extension, in case you ever need to change it back.