This article describes some causes and steps to take when Firefox takes a long time to start up. *If Firefox does not start up at all, see [[Firefox will not start]]. __TOC__ {for win, fx35} = Outdated Firefox version = Firefox 3.5 may take an abnormally long amount of time to start after turning on your computer (this is known as a "cold start"). Thus is caused by a bug which was '''fixed in Firefox 3.5.1'''. Updating Firefox will fix the problem. # At the top of the Firefox window, click on the {menu Help} menu. # Select {menu Check for Updates...}. # Follow the instructions in the Firefox Update wizard. For more information, see [[Updating Firefox]]. {/for} = Home page = Problems with a website can cause Firefox to take a long time to start. Try changing your Firefox home page to a different website or use a blank home page. See [[How to set the home page]] for instructions. <!-- https://support.mozilla.com/questions/776797 and https://blog.mozilla.com/tglek/2010/10/04/diagnosing-slow-startup --> = 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. <!-- https://blog.mozilla.com/tglek/2010/10/04/diagnosing-slow-startup --> {for win} = Large numbers of fonts = Firefox loads all your fonts so that it can allow websites to display pages in all available fonts. Having large numbers of fonts can slow down this process. Removing unused fonts can sometimes greatly speed up Firefox startup times. <!-- Bug 502821 and Bug 491283 --> {/for} = Extensions or themes = Firefox loads extensions when it starts up and many extensions themselves add startup tasks. See [[Troubleshooting extensions and themes]] for steps on how to identify the extension that may be causing the problem. = Other causes = [[Basic troubleshooting]] steps can help diagnose and isolate the cause of this issue.

This article describes some causes and steps to take when Firefox takes a long time to start up.

• If Firefox does not start up at all, see Firefox won't start - find solutions.

Home page

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

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.

Extensions or themes

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

Other causes

Basic troubleshooting steps can help diagnose and isolate the cause of this issue.