Firefox sometimes uses more memory (RAM) than it should. This can make Firefox slower, and in extreme cases, it can even make Firefox crash. Memory use by any program is affected by many factors, such as memory leaks, conflicting third party programs, and usage patterns. This article describes how to make Firefox use less memory. __TOC__ = Add-ons = == Extensions and themes == Extensions and themes can cause Firefox to use more memory than it normally would. To determine if an extension or theme is causing Firefox to use too much memory, start Firefox in its [[Safe Mode]] and observing its memory usage. In Safe Mode, extensions and themes are disabled, so if you notice a significant improvement, you can try disabling or uninstalling extensions. * For more information on starting Firefox in Safe Mode and on how to find which extension or theme is causing your problem, see [[Troubleshooting extensions and themes]]. == Plugins == Plugins to display special types of content can consume large amounts of memory, especially older versions. You can test to see whether one of your plugins is causing Firefox to use too much memory by selectively disabling some of them: # {for win,linux}At the top of the Firefox window{/for}{for mac}On the menu bar{/for}, click the {menu Tools} menu, and select {menu Add-ons}. The Add-ons menu will appear. # Select on the {menu Plugins} panel. # Click on a plugin in the list to select it, then press {button Disable} to disable it. # Repeat for some of the plugins in your list. After disabling some of your plugins, close and restart Firefox, and observe its memory usage. If you don't see an improvement, you can enable those plugins again and try with a different set. If you do see an improvement in Firefox's memory usage after disabling a certain plugin, you may leave it disabled or try to see if there is an update for it. [[Popular plugins]] lists several plugins and how to install the latest version of each. <!-- Commented out for monkey reasons. = Settings that reduce memory usage = Firefox has hidden settings that let you change how it uses memory. == Memory cache == Firefox caches image and interface data in memory so they can be displayed quickly. You can see how much memory Firefox uses for this purpose. # Type '''about:cache''' in the Location Bar at the top of the Firefox window and press {for win,linux}{key Enter}{/for}{for mac}{key Return}{/for}. # A page listing your Firefox cache information should appear. Under the '''Memory cache device''' heading, '''Maximum storage size''' refers to the maximum amount of memory Firefox will use for this purpose, and '''Storage in use''' refers to the current amount of memory Firefox is using for this purpose. By default, Firefox will use more memory on computers with more memory installed. You can change the limit for your computer. ;:{note}'''Lowering the amount of memory available for caching will increase the amount of time Firefox takes to display web pages and dialogs.'''{/note} # [[T:aboutconfig]] # The about:config page should appear. {for win,linux}Right-click{/for}{for mac}Hold down the {key Ctrl} key while you click{/for} in the main part of the window, then select {menu New}, and then slect {menu Integer}.<br/> <br/>[[Image:highmemusage-newinteger.png]] <br/> <br/> # When prompted, type {pref browser.cache.memory.capacity} and press {button OK}. # Next, type the maximum number of kilobytes you want Firefox to use for cache and press {button OK}. If you want to set the preference back to its default value: # [[T:aboutconfig]] # Search for the preference {pref browser.cache.memory.capacity}. # {for win,linux}Right-click{/for}{for mac}Hold down the {key Ctrl} key while you click{/for} the entry for browser.cache.memory.capacity and press {menu Reset}. == Cached previously viewed pages == Firefox stores pages in memory so they can be displayed quickly when you press Back or Forward. By default, Firefox will use more memory on computers that have more memory installed. You can change the maximum number of pages Firefox will store for this purpose on your computer. ;:{note}'''Lowering the number of stored pages will slow down Firefox when you press Back or Forward.'''{/note} # [[T:aboutconfig]] # The about:config page should appear. Search for the preference {pref browser.sessionhistory.max_total_viewers}, and double-click on it. # In the browser.sessionhistory.max_total_viewers prompt, type the maximum number of pages you want Firefox to store and press {button OK}. If you want to set the preference back to its default value: # [[T:aboutconfig]] # Search for the preference {pref browser.sessionhistory.max_total_viewers}. # {for win,linux}Right-click{/for}{for mac}Hold down the {key Ctrl} key while you click{/for} the entry for browser.sessionhistory.max_total_viewers and press {menu Reset}. {for win} == Behavior on minimize == By default, Firefox will allow Windows to reclaim its memory when Windows needs it for other programs. Firefox can be configured to allow Windows to reclaim its memory immediately. ;:{note}'''Allowing Windows to reclaim the memory immediately will make Firefox slower to come up after being minimized.'''{/note} # [[T:aboutconfig]] # The about:config page should appear. Right-click anywhere in the grid and choose {menu New}, then {menu Boolean}. # In the Enter the preference name prompt, type {pref config.trim_on_minimize} and press {button OK}. # Next, choose {pref True} and press {button OK}. If you want to set the preference back to its default value: # [[T:aboutconfig]] # Search for the preference {pref config.trim_on_minimize}. # Right-click the entry for config.trim_on_minimize and press {menu Reset}. {/for} --> = Restarting Firefox = Firefox's memory usage may increase if it's left open for long periods of time. A workaround for this is to periodically restart Firefox. You can configure Firefox to save your tabs and windows so that when you start it again, you can start where you left off. See [[Session Restore]] for details. = Using fewer tabs = Each tab requires Firefox to store a web page in memory. If you frequently have '''more than 100 tabs open''', consider using a more lightweight mechanism to keep track of pages to read and things to do, such as: * [[Bookmarks|Bookmarks]]. ''Hint: "[[Tabbed Browsing#Bookmarks and Tabbed Browsing|Bookmark All Tabs]]" will bookmark a set of tabs.'' * [http://lifehacker.com/378062/five-best-gtd-applications To-do list applications]. = Memory troubleshooting tools = <!-- Memory issues can be difficult to troubleshoot because they are normally visible only in aggregate. Furthermore, there are four broad categories of bugs that can lead to high memory use, which can be hard to distinguish. * ''Bloat'', or using a large amount of memory to store a small amount of information. (Goes away when you close each tab.) * ''Caching'', or intentionally remembering something for a limited time in case it is needed again. (Usually less than 100MB.) * ''Fragmentation'', or failing to re-use free memory. (Usually limited to 2X.) * ''Leaking'', or continuing to store data in memory after it is no longer needed. --> Firefox developers have written two extensions to help users isolate leak bugs: * '''[https://addons.mozilla.org/firefox/addon/2490 Leak Monitor]''' : Can alert you immediately when certain types of leaks occur. This makes it easier to figure out what triggers these leaks. * '''[https://addons.mozilla.org/firefox/addon/5972 RAMBack]''': Lets you flush many of Firefox's caches, allowing you to distinguish caching from leaking. If you're a C++ programmer, you can even try your hand at some of the [https://wiki.mozilla.org/Performance:Leak_Tools tools Firefox developers use to debug leaks]. <!-- Jesse Ruderman would be happy to walk users through setting up trace-refcnt! --> <!-- MZ credit --> <br/> <br/> '''''Based on information from [http://kb.mozillazine.org/Reducing_memory_usage_-_Firefox Reducing memory usage - Firefox (mozillaZine KB)]'''''

Firefox sometimes uses more memory (RAM) than it should. This can make Firefox slower, and in extreme cases, it can even make Firefox crash.

Memory use by any program is affected by many factors, such as memory leaks, conflicting third party programs, and usage patterns. This article describes how to make Firefox use less memory.

Add-ons

Extensions and themes

Extensions and themes can cause Firefox to use more memory than it normally would.

To determine if an extension or theme is causing Firefox to use too much memory, start Firefox in its Diagnose Firefox issues using Troubleshoot Mode and observing its memory usage. In Safe Mode, extensions and themes are disabled, so if you notice a significant improvement, you can try disabling or uninstalling extensions.

• For more information on starting Firefox in Safe Mode and on how to find which extension or theme is causing your problem, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Plugins

Plugins to display special types of content can consume large amounts of memory, especially older versions.

You can test to see whether one of your plugins is causing Firefox to use too much memory by selectively disabling some of them:

1. At the top of the Firefox windowOn the menu bar, click the Tools menu, and select Add-ons. The Add-ons menu will appear.
2. Select on the Plugins panel.
3. Click on a plugin in the list to select it, then press Disable to disable it.
4. Repeat for some of the plugins in your list.

After disabling some of your plugins, close and restart Firefox, and observe its memory usage. If you don't see an improvement, you can enable those plugins again and try with a different set.

If you do see an improvement in Firefox's memory usage after disabling a certain plugin, you may leave it disabled or try to see if there is an update for it. Use plugins to play audio, video, games and more lists several plugins and how to install the latest version of each.

Restarting Firefox

Firefox's memory usage may increase if it's left open for long periods of time. A workaround for this is to periodically restart Firefox. You can configure Firefox to save your tabs and windows so that when you start it again, you can start where you left off. See Restore previous session - Configure when Firefox shows your most recent tabs and windows for details.

Using fewer tabs

Each tab requires Firefox to store a web page in memory. If you frequently have more than 100 tabs open, consider using a more lightweight mechanism to keep track of pages to read and things to do, such as:

• Bookmarks. Hint: "Bookmark All Tabs" will bookmark a set of tabs.
• To-do list applications.

Memory troubleshooting tools

Firefox developers have written two extensions to help users isolate leak bugs:

• Leak Monitor : Can alert you immediately when certain types of leaks occur. This makes it easier to figure out what triggers these leaks.
• RAMBack: Lets you flush many of Firefox's caches, allowing you to distinguish caching from leaking.

If you're a C++ programmer, you can even try your hand at some of the tools Firefox developers use to debug leaks.

Based on information from Reducing memory usage - Firefox (mozillaZine KB)