The power user's guide to Firefox

About about:config

If you type

about:config

into the Firefox Location bar and press return, you’ll see a list of hundreds of options that you can modify right from the browser window (see “About This Browser”)—and most of them can’t be adjusted in Firefox’s Preferences menu. They range from the way your mouse works to obscure network settings. ( Click here for a full list of these options.)

The about:config window displays the name, status, type (Boolean, integer, or string), and value for each option. To change a Boolean (true or false) value, double-click on it; for other options, double-click on the row and then enter a new setting. You can control-click (or right-click) on a value to reset it; from the resulting contextual menu, you can also add, copy, or modify values.

For example, you can use the about:config page to activate a feature called pipelining, which sends multiple HTTP requests at once. With fast Internet connections, this can dramatically speed up page loading, as different page elements can load at the same time. To turn on pipelining, double-click on network.http.pipelining to set its value to true; do the same for network.http.proxy.pipelining. Next, double-click on network.http.pipelining.maxrequests and enter the number of simultaneous requests you’d like to send (try entering

as a starting point).

About This Browser To see hundreds of hidden Firefox preferences that you can modify, enter about:config in the Location bar.
(Click image to open full screenshot)

You can also add new options if they aren’t already on the list. For example, to block Flash-based sites from opening pop-up windows, control-click (or right-click) anywhere on the page and choose New: Integer from the contextual menu. Enter

privacy.popups.disable _from_plugins

as the preference name. For the value, enter

Here’s another option you can add: By default, Firefox waits 250 milliseconds before beginning to display a page (allowing more of the page to load into memory first). You may be able to speed up page rendering by removing this delay. Control-click (or right-click) anywhere on the about:config page and choose New: Integer from the contextual menu. Enter

nglayout.initialpaint.delay

as the preference name and

as its value. The amount of improvement (if any) will depend on the speed of your machine and Internet connection; try it out and see if it helps.

But heed two warnings before you dive in: First, some of the about:config settings have no effect in OS X. Second, the about:config window gives you a lot of power, with which you can cause a lot of damage (including utterly disabling Firefox). So be careful. Before you do anything else, back up the Firefox folder in / your user folder / Library/Application Support.

Changes you make will take effect when you restart Firefox. To undo a change you made, control-click (or right-click) on the setting and choose Reset from the contextual menu. Firefox will return the setting to its default value; if it was a setting you added, it will be given a blank value and will disappear when you quit Firefox.