Change the Default App for a File Type on Mac

You install a better PDF reader, and every PDF still opens in Preview. macOS decides which app opens a file by its type, and the setting to change that default is hidden inside Get Info — one button applies your choice to every file of the kind at once.

Change the default for a whole file type

1. In Finder, select any file of the type you want to reassign — one .pdf, one .jpg, one .md — and press Cmd+I to open Get Info.
2. Expand the Open with: section and pick the app you want from the pop-up menu. If it is not listed, choose Other… and select it from Applications.
3. Click Change All…, then Continue in the confirmation dialog.

Every file with the same extension now opens in your chosen app, and the change survives restarts. Undoing it is the same three steps with the old app selected — pick Preview again, click Change All, done.

Note the default is per file type, not per app: setting .jpg to open in Pixelmator does nothing for .png. Repeat the process for each extension you care about.

Open one file in a different app, once or always

For a one-off, do not change anything system-wide:

• Control-click the file and choose Open With, then pick the app. This opens the file once without changing any defaults.
• Hold Option while the Open With submenu is showing and the command becomes Always Open With — that sets the default for this one file only, leaving the rest of the type alone.
• Dragging a file onto an app's Dock or toolbar icon also opens it there once. If the icon will not accept the drop, hold Option+Cmd while dropping to force it.

The per-file override from Always Open With is stored with that file, which explains a common mystery: one stubborn document that ignores your Change All setting probably has an old per-file override. Fix it with Get Info on that file — set the app and skip the Change All button.

Special cases: browser and email

Two defaults do not live in Get Info. The default web browser is set in System Settings → Desktop & Dock → Default web browser. The default email app is set inside Apple Mail: Mail → Settings → General → Default email reader. Both handle links (https://, mailto:) rather than file types, which is why they are configured elsewhere.

When files revert or open in a deleted app

If you uninstalled an app and its old files now show a blank icon or complain the app cannot be found, run Change All with a real app selected — that rewrites the binding. If defaults seem to randomly revert (an app update or a newly installed app grabbing a type), just reapply Change All; your explicit choice wins over an app's registration.

As a last resort, you can rebuild the Launch Services database that stores all of these bindings:

# rebuild the default-app database (safe; takes a minute)
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user

# then relaunch Finder
killall Finder

This resets every custom default back to macOS's own choices — there is no direct undo, so treat it as a fix for genuine corruption (duplicate "Open With" entries, ghost apps), not routine cleanup, and expect to redo your Change All picks afterwards.

Related: apps macOS refuses to open

If your newly chosen app triggers an "unidentified developer" warning the first time, that is Gatekeeper, not a broken default. Our guide to opening apps from unidentified developers explains the safe way through.