I have to admit that while I do not agree with every decision Mozilla makes in regards to Firefox, I can't really complain about the web browser's performance on my system. It is as stable as it gets, does not use too much memory or cpu, and is a pleasure to work with. While I do my best o ensure that, for instance by running it without plugins and with NoScript, it is the complete package that makes the difference.
This was not always the case, especially during the Firefox 4 days when the browser started to eat memory like crazy. If you are running Firefox currently and notice it slowing down considerable over time or right away, I suggest you try the following fixes to resolve the issue.
Speed up Firefox
This may sound like the most obvious thing and it is. Mozilla spend engineering time on optimizations and they began to show recently resulting in a leaner, slimmer and faster browser. If you are still running an older version of Firefox, try upgrading to the latest version by downloading it from Mozilla or using the internal updater.
If you notice slow downs after an upgrade, consider down grading, or switching to another release channel. If you are running the stable version of Firefox, chance is you will receive a fix in six weeks. If you run a beta, aurora or nightly version, you will receive the fix much faster as these versions are updated more frequently.
Load about:addons, switch to plugins and disable all plugins you do not need. While you may need Shockwave Flash, Silverlight or Java, you - very likely - won't need the rest listed here.
When you have disabled the plugins you do not need, head over to Mozilla's plugincheck website and see if updates are available for the plugins you use.
You can alternatively enable click to play in the browser. Do the following to enable click to play
- Enter about:config in the browser's address bar
- Confirm you will be careful if you see the warning screen.
- Search for plugins.click_to_play
- Double-click to set it to true to enable it.
3. Add-ons and Themes
If you have many add-ons and themes installed, it may be because of some of them that Firefox is slower than it should be. I'd suggest you go through the list of installed add-ons and themes to see if there are some that you do not really need anymore to uninstall them from the browser.
You can load about:addons again to browse the add-ons under Extensions and themes under Appearance on the page. One suggestion would be to disable all addons and themes for a short while to see if this resolves your issues with Firefox. You can either do that manually by disabling all add-ons and themes or with a click on Firefox > Help > Restart with Add-ons disabled.
If you have installed Greasemonkey or Scriptish in the browser and make use of userscripts, they may also be the culprit depending on what they do. Try disabling them to see if it resolves your issue. If it does, try and find alternatives for the scripts either in form of other userscripts or extensions.
5. Slow on load
If Firefox is slow when it is loading you may want to consider the following configuration changes. Click on Firefox > Options, switch to Tabs there and make sure "Don't load tabs until selected" is enabled. This loads the tabs when you click on them and not on the start of the browser.
If you happen to open lots of tabs during a browsing session consider installing the Unload Tab add-on for Firefox. It unloads tabs after a certain amount of inactivity to free up resources.
6. Clear temporary data
Firefox saves previously visited web pages to the cache from where they are loaded. While this speeds up future web browsing, it sometimes may result in errors, for instance when a cached page is loaded that is either out of date or corrupt. You may want to clear the browsing data regularly because of that. Data that is saved by Firefox is also increasing the size of the databases the browser has to load.
The easiest way to clear the history is to press Ctrl-Shift-Del and delete the cache as well as the browsing data and download history.
If you notice slow downs on a particular site, you can remove information that Firefox has stored about that site only. To do so press Ctrl-Shift-H to open the History window, right-click a history entry and select Forget About This Site.
7. Modified Preferences
Sometimes a preference may be responsible for Firefox being slower than it should be. You can load the about:support page when the browser is open to get a list of all preferences that have been modified (that are not in their original state). While most may not have an effect on the browser's performance, some like browser.cache or network parameters may have.
Firefox makes use of hardware acceleration to render some contents faster. It is advised to update the video card driver regularly because of this. You may also want to make sure that hardware acceleration is enabled.
For Flash, right-click on any Flash contents and select Settings from the context menu.
To check if Firefox is using hardware acceleration, click on Firefox > Options, switch to the Advanced > General tab and see if "Use hardware acceleration when available" is enabled.
9. New Profile
To find out if the slowness is linked to the profile you are currently using, try creating a new profile and use it for a while to see if it is faster than the current one.
To do so start Firefox with the parameter --profilemanager and use the window that opens up to create a new profile. Click on the create profile button to do so.
10. Reset Firefox
If a new profile helped you, you may want to consider resetting Firefox. This resets Firefox to its default state while part of the data that you have saved to it remains accessible. Firefox will save bookmarks, browsing history, passwords, cookies and web form information for you, but not extensions, themes or advanced configuration changes. While the old profile gets saved to the desktop in the process, you will spend some time recovering add-ons and settings that you do not want to live without.
To reset Firefox hold down Shift while you start it and select the reset option on the loading screen. You can alternatively select Firefox > Help > Troubleshooting Information and there Reset Firefox to do so.