Simple steps to greatly improve the startup time of Firefox.
Compatibility 
Works with: Firefox 3.6+
Background
Overtime users notice Firefox seems to take a longer to startup. This is especially noticeable if working with a fresh install of Firefox on another computer.
The Tweak
There are two parts to this tweak, clearing out Temporary Files (Windows users only) and vacuuming the places.sqlite database. After performing these tweaks, users should notice several things:
- Reduction in the size of the places.SQLite database file
- Faster cold start up
- Faster warm (restart) start up
- Better performance from the Awesome Bar
Cleaning Up Temporary Files (Windows Only)
Part of the slow down in Firefox is due to a change in how Firefox gets the randomness it needs for security purposes on Windows. The procedure involves scanning some temporary folders looking for bits normally added by OS and other applications operations. Firefox 3.5 looks for more files and deeper (more sub-folders) for increased randomness, but it has led to unexpected results for users with too many temporary folders or files resulting in slow startups. This is a known bug Bug 501605 and this may have been addressed in recent updates.
Window is a pack-rat and has a hard time letting go of files it is no longer using. As a result you can end up with a very large and sizable folder. There are two parts to this cleaning up process, Windows Temporary Files and Internet Explorer’s Temporary Files.
Cleaning out Windows Temporary Files
Windows XP users should delete ALL (some may be in use and therefore can not be removed) the files within these folders:
- C:\Documents and Settings\*user*\Local Settings\History
- C:\Documents and Settings\*user*\Local Settings\Temporary Internet Files
- C:\Documents and Settings\*user*\My Recent Documents
- C:\Documents and Settings\*user*\Temp\
Windows Vista and 7 users can not easily get to their temporary files via Windows Explorer. There are a couple ways you can clean out your temporary files. You can use the Disk Cleanup Tool which comes with Vista via clicking the Start button, clicking All Programs, clicking Accessories, clicking System Tools, and then clicking Disk Cleanup. A quicker method is getting to the Temporary Files folder itself by clicking the Start button then typing %Temp% in the Start Menu command box. This will open an explorer window showing the content of your Temporary Files folder. From here press CTRL+A to select all then press Delete. You will get the usual warning dialog box about deleting files, click Yes. Again, any files that are in use you will not be able to remove, but this only should be a small handful of files.
Cleaning out Internet Explorer Temporary Files
Note: This only removes Internet Explorer’s temporary files, this will not affect your settings in Firefox. Much like Windows, Internet Explorer holds on to files as well. But in the case of Internet Explorer it is so pages will load faster the next time you visit. There are a couple ways to clear out this content. If Internet Explore is running, go to Tools, Internet Options. Look for a Temporary Internet Files or Browsing History section with an options to Delete. If you don’t have Internet Explorer running or care not to run it, you can get to the Internet Options via the Windows Control Panel. Warning: Having a large number of Temporary Internet Files may cause the Internet Options window and/or Windows to be unresponsive for anywhere up to a couple minutes.
Vacuuming Your places.sqlite Database (All Platforms) Firefox 3.6 ONLY
Much like your hard drive when adding and removing content, your Firefox databases can become fragmented resulting in both bloated database files as well as slow access times. places.sqlite can come become quite bloated with the recent changes to the default history time span, being raised from 9 to 90 days. This can be fixed very quickly and easily by vacuuming your places.sqlite Firefox databases.
There is a Firefox Extension which does this for you. Vacuum Places Improved allows users to vacuum the places.sqlite databases from within the browser. Plus it can be configured to automatically vacuum after a given number of starts or display a reminder (vacuum icon on the status bar) after a given number of starts.
Notes
Firefox 4 introduced improved management of the places.sqlite database and vacuuming this database file is no longer needed and can actually degrade performance if done frequently.
Updated: November 15, 2025
