To always show file extensions on your Mac, go to Finder > Settings > Advanced and select “Show all filename extensions.” This changes how filenames are displayed—you do not need to rename any files.
Turn on file extensions in Finder
- Open Finder and choose Finder > Settings from the menu bar at the top of the screen.
- Click Advanced.
- Select “Show all filename extensions.”
With this option enabled, extensions appear even for files with “Hide extension” selected individually. If you turn it off, whether an extension appears depends on each file’s individual setting. These steps and behavior are described in Apple’s guide to showing or hiding filename extensions.
Which part of a filename is the extension?
Take the example filename travel-photo.jpg: travel-photo is the main part of the name, while .jpg is the extension. The extension is the ending of the full filename and indicates the file type and which apps can open it.
Making an extension visible is different from changing its characters. You do not need to manually add .jpg or another extension to a filename just to display its existing extension.
Keep the extension when renaming a file
To change only the name, rename travel-photo.jpg to something like hanoi-photo.jpg, leaving the extension intact. Changing the extension as well may prevent the app that created the file from opening it.
As a precaution, you can also select “Show warning before changing an extension” in the same Advanced settings. This option is described in Apple’s Finder settings guide. It provides a warning rather than locking the extension against changes.
The steps and menu labels above follow Apple’s macOS 27 documentation.
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