If you recently switched to Firefox from another browser, you might not be aware of all the available about: config settings that you can change or add to customize Firefox. Since I recently got a new computer and had to install Firefox, I decided to take another look at the the config settings and review which ones I apply the most. What follows then is my personal favorite config changes and why I implement them.

To access the config screen, open Firefox and type in about:config for the url and enter. You will be greeted with a long list of settings and their values. Some of these settings might not appear on the list, so you will have to add them.

Browser Memory:

browser.cache.memory.capacity – This integer setting specifies how much RAM, Firefox can use to cache itself. For computers with 512MB of RAM, set this to 32768, if you have less physical memory than try 16384. And of course if you have more than 512, try a higher value. A value of -1 tells Firefox to automatically manage this setting. The new setting for 2.0 Firefox is actually browser.cache.disk.capacity.

browser.cache.memory.enable – This boolean setting must be set to true in order for Firefox to use memory for cache, so if you are going to use the previous setting, make sure this is set to true.

config.trim_on_minimize – For Windows users only, this boolean setting specifies if Firefox should reduce its memory usage when minimized to the Taskbar. Changing this to false will speed up minimizing and mazimizing of Firefox.

Popup Windows:

dom.popup_maximum – This integer setting determines the maximum number of simultaneous popup windows which can be open at any time. The default is 20, which is pretty high, so a more conservative value like 8, 6, 4, or even 2 would be more appropiate, depending on your browsing habits.

dom.disable_window_open_feature.close – This is an essential boolean setting that forces all popup windows to include a close button is set to true. Helpful because, so many popups deliberately disable the close button.

dom.disable_window_open_feature.close.resizeable – This boolean setting if set to true enables popups to display resize controls. Helpful for sites that show popups that are too large for your screen resolution.

Browser Speed Settings:

nglayout.initialpaint.delay – Adding this integer setting will allow you to change the amount of time Firefox should wait before it starts to display a web site. The default is 250, but some users prefer a setting of zero, or perhaps a smaller value like 60. Changing this setting should seem obvious if you have a high speed connection.

The following settings increase network connections to the web server, which some webmasters may frown upon, so do not implement these changes without understanding that more connections do in fact increase the load on web sites you visit. If you are connected through a proxy server, there are separate settings for this that are not covered here, see the additional links for more information.

network.http.max-connections – This integer setting determines how many simultaneous HTTP connections can be made. The default is 24, but if you have a broadband connection, you can attempt a value of 48, 72, or even 96. This is the max number of connections, it does not mean that Firefox will create 48 connection at once.

network.http.max-connections-per-server – This integer setting determines how many simultaneous connections can be made to a single server. Firefox defaults to 8, but broadband users can increase the value to 16 or even 32. However excessive connections to the web server could be seen as an attack on the website, similar to a DDoS attack and you may have problems connecting to some sites.

network.http.pipelining – This boolean setting enables what is called HTTP Pipeling, which is a feature that not all web servers support, but which does increase browser downloads. If you experience unusual problems after setting this to true, you should set this setting back to false to avoid connection issues with certain websites.

network.prefetch-next – Usually you would want to enable a feature that offers some speed benefit, but some users find Google Prefetching to be controversial, because it allows your browser to go to certain sites without your approval and without you seeing it. It is done in the background and based on what Google thinks you want to go. Some see this as a security issue and recommend disabling it, by setting the value to false.

For Firefox 2.0:

browser.urlbar.hideGoButton – In Firefox 2.0, the GO button was changed to a green arrow. Many people like to remove the GO button. However for some reason Firefox 2.0 does not let you do this via the Customize Toolbar interface; there are plans to fix this at a later update. If you change this boolean setting to true, it will make the arrow disappear.

browser.tabs.closeButtons – You can change the way the close button is implemented on tabs. Your choices range from 0 thru 3.

  • 0 – Display a close button on the active tab only.
  • 1 – Display a close button on each tab (default).
  • 2 – Don’t display any close buttons.
  • 3 – Display a single close button at the end of the tab bar.

More Resources:

If you would like to learn more about Firefox, see the following sites for more information and details.

TweakGuides Firefox Guide is perhaps the best all around guide on tweaking Firefox.

MozDev Documented Preferences is the most comprehensive list of config preferences you can find on the Internet.

Mozillazine Forums are also a good place to post questions or find answers on all things Firefox related.