When you launch a Mac application that you use regularly, and it won't start up, or it never finishes launching, you're bound to be frustrated. If you're lucky, this is a one-time event. You can force quit the app and try again, hopefully with success.

If the app still doesn't start, there are several fixes you can use to solve why your Mac suddenly can't open the application.

The information in this article applies macOS Catalina (10.15) through OS X Lion (10.10), except as indicated.

Reasons a Mac Application Won't Start

If you've been running the app that won't start for a while successfully, and now it won't start, something changed.

• There's a chance a file became corrupt because of a system crash.
• The app may need to be updated.
• It may be conflicting with another app.
• The app's permissions or preferences file may be damaged.

How to Fix Applications Not Opening on Mac

Whatever the reason, there are several possible fixes for this problem, ranging from simple to more complex.

1. Restart the Mac. It's always smart to start with the simplest fix possible.

2. Update the app. Check that you have the most current version of the app, and if not, update it by using the Mac App Store. This step is essential following an update to the Mac operating system. In many cases, updating the affected app cures the problem.

3. Delete the app preference file (plist file). You can delete this file manually or with a Mac app uninstaller like AppDelete. Plist files can become corrupt when a Mac shuts down or restarts unexpectedly or when an app freezes or crashes. As a result, the app may not open.

   When you delete a bad preference file, your Mac creates a new plist file that contains all the app's defaults automatically. You have to reconfigure the app's preferences afterward.

   To locate and remove preference files:

   1. Go toFinder> Library > Preferences.
   2. Look for the plist in this format:com.developer_name.app_name.plist.
   3. Delete the plist file that matches the app.

   Apple hides the Library folder by default so that you can't accidentally make changes to it. You need to know how to show hidden files and folders on a Mac if you don't see the Library folder on your Mac.

4. Start your Mac in Safe Mode. This troubleshooting startup environment restricts most startup items. It also limits the operating system to use only the basic OS core. If you can start the Mac in Safe Mode and then use the app in question, the likely cause is not permissions or preference files. The conflict may come from another app or a startup item.

5. Use Disk Utility to repair app permissions. In OS X Yosemite and earlier, one of the first things to do when encountering an app that won't launch is to repair permissions. This step ensures the application and any associated files it needs have the correct permissions required to run.

   You don't need to know what the permissions should be. Your Mac keeps a database of the default permissions for most applications you install.

   With the release of OS X El Capitan, Apple added a new feature that made manually repairing file permissions no longer necessary. File permissions are automatically repaired with software updates in OS X 10.11 and later.

6. Reinstall the app. After checking the App Store to verify the app is still available, delete the problem app from your Mac. Then reinstall it from the App Store.

7. Contact the app developer. Visit the app developer's website and look for notes about compatibility with your version of macOS or OS X or other apps and services you use.

• How do I check if a Mac app that's not opening is an old version?

  Open the Finder on the Mac and select the application. Press the spacebar to open a Quicklook window, which includes the version number of the app. Open the Mac App Store and search for the app. If a newer version is available, download it.

• What does it mean when a Mac app icon bounces up and down but the app never opens??

  A bouncing icon usually means the app is trying to get your attention. Look for a small dialog box somewhere on your screen. The app may need you to enter a password or some other information before it can launch.