This article describes some causes of a long start up time and steps you can take to improve it.

• If Firefox starts but isn't responsive, see Firefox hangs or is not responding - How to fix.
• If Firefox does not start up at all, see Firefox won't start - find solutions.

Change the home page

Problems with a website can cause Firefox to take a long time to start. Try changing your Firefox home page to the default home page or a blank page. See How to set the home page for instructions.

Change how windows and tabs are loaded

If you set Firefox to use the Session Restore feature to show your windows and tabs from last time, Firefox can take a long time to start if you had lots of websites open the last time you used Firefox. You can choose to open the last selected tab only:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Select the General panel
3. Check Don't load tabs until selected so that only the last selected tab is loaded at startup (this should be the default setting).

Check your antivirus software

Firefox reads a number of files normally during startup. Some antivirus software may do intensive scans of each of these files during startup and block access until those scans complete. If the problem began after installing, updating, or reconfiguring your antivirus software, contact the software provider for assistance.

Troubleshoot extensions or themes

Firefox loads extensions when it starts up and many extensions add startup tasks. See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems for steps on how to identify an extension that may be causing the problem.