How to Change Default Applications and File Associations in macOS

Whenever you double-click a file on your Mac, macOS determines which software handles that file type based on its LaunchServices file association database. After installing new creative tools, text editors, or media suites, macOS frequently defaults to native Apple utilities—opening high-resolution MKV videos in QuickTime Player (which often fails with codec errors), launching PDF forms in Apple Books instead of Preview or Adobe Acrobat, or routing source code files into Xcode instead of VS Code. In macOS, users can configure file associations on an individual file basis, execute permanent system-wide overrides across all files of a specific extension, and customize system default browsers and email clients without touching the terminal.

Setting Default File Associations Using the Get Info Window

The primary and most permanent method to remap default applications for any file extension (such as .pdf, .mp4, .docx, or .png) is through Finder’s Get Info inspector:

1. Open Finder and locate an example file with the extension you wish to reassign (for example, a .pdf document).
2. Right-click (or hold Control and click) the file and select Get Info. Alternatively, highlight the file and press Command + I.
3. In the Info window that appears, locate the section titled Open with. If the section is collapsed, click the small grey arrow to expand it.
4. Click the drop-down menu to view a list of all installed applications capable of reading that file type.
5. Select your preferred default application (for example, choose Preview, Adobe Acrobat, or PDF Expert).
6. To apply this software choice to every single file sharing this file extension across your entire Mac, click the Change All… button located directly beneath the drop-down menu.
7. A confirmation prompt will ask: “Are you sure you want to change all similar documents to open with the application?” Click Continue. All files sharing that extension will now launch in your chosen application automatically.

Temporarily Opening Files with an Alternative Application

When you need to inspect a file in a specialized editor once without permanently altering your system-wide file associations:

• Open With Context Menu: Right-click the file in Finder, hover over Open With, and select any compatible software from the sub-menu.
• One-Time Permanent Override: If you want one specific project file to always open in a specialized editor (while leaving all other files of that extension opening in the system default), open Get Info (Command + I), choose the software under Open with, but do not click Change All. macOS binds the specific file’s metadata to that chosen app without affecting other documents.

Configuring Default Web Browser and Email Clients in System Settings

System protocols such as web links (http://, https://) and email links (mailto:) are governed separately from individual file extensions:

1. Click the Apple menu (&apple;) in the top-left corner and open System Settings.
2. Select Desktop & Dock from the left-hand navigation pane.
3. Scroll down to the Windows & Apps section to locate the Default web browser drop-down menu.
4. Select your preferred everyday browser (such as Safari, Google Chrome, Mozilla Firefox, or Microsoft Edge). All clicked web links from emails, documents, and chats will now open in this browser.
5. To change your default email client: Open the native Mail app, click Mail > Settings in the top menu bar, go to the General tab, and select your preferred application from the Default email reader dropdown (e.g., Microsoft Outlook or Spark).

Troubleshooting Duplicate App Entries in the Open With Menu

Over time, installing app updates, testing beta builds, or retaining external backup drives can cause macOS LaunchServices to display duplicate or dead application shortcuts in the “Open With” menu. To reset and clean the LaunchServices database:

1. Open the Terminal app on your Mac (press Command + Space, type Terminal, and press Enter).
2. Execute the official LaunchServices registration rebuild command:
   /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
3. Restart Finder by typing:
   killall Finder
4. Right-click any file in Finder. The “Open With” menu will now display clean, deduplicated application lists reflecting only currently installed software.

Configuring proper default applications and file associations streamlines daily navigation in macOS, ensuring your documents, media, and web links open seamlessly in the tools best suited to your workflow.