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Want to increase your Download speeds in Firefox? Have pages display faster? This may be the True How To for you!

Scope:

The purpose of this "True How To" is to allow you to maximize the power of the Mozilla Firefox browser to get webpages to open faster and increase download speed.

Versions Tested: 

1. Backup Settings

First make a backup of your preferences in Firefox, just make a copy of the file prefs.js, which is kept in your Firefox profile folder. If something happens, you can always copy this file back. (Shut down Firefox before making a copy of prefs.js or moving a copy back into the profile folder!)

In Windows XP, the profile folder is


\Documents and Settings\\Application Data\Mozilla\Firefox\Profiles\.default\

In Windows Vista, this folder is
\Users\\AppData\Roaming\Mozilla\Firefox\Profiles\.default\

You can also search for the prefs.js in other operating systems. In Linux it will likely be in the/usr/lib/mozilla-VERSION/defaults/pref/ directory called all-redhat.js or a variation of that. You may want to back up the pref directory as well.

2. Configure your Mozilla Firefox Browser

Type about:config in the address bar in the Firefox browser and press Enter.

 If you double-click on an entry that has a Boolean value, it will just switch from true to false. If you want to be certain that changes take effect, be sure to close and reopen Firefox after making a change. Not every setting in about:config exists by default. Some of them have to be created manually. If you want to add a new preference, right-click somewhere on the page and select New, then select the type of item to create (String, Integer or Boolean) and supply the name and value.

3. Speeding up webpage display

Creating an nglayout.initialpaint.delay integer preference lets you control latentcy of Firefox opening a page. Firefox defaults it to 250 milliseconds, or 0.25 of a second. Setting it to 30 to 50 (milliseconds) causes most pages to show up faster.

Reduce the number of reflows

When Firefox is loading a page, it reformats or "reflows" the page, based on what data has been received. Create a content.notify.interval integer preference to control the minimum number of microseconds (millionths of a second) that elapse between reflows. Reflows may make the browser feel a bit slow, increase the interval between reflows by raising this to500000 or even to 1000000. If you set this value, be sure to also create a Boolean value called content.notify.ontimer and set it to true.

Control Firefox's 'unresponsive' time

When rendering a page, Firefox periodically runs a little faster internally to speed up the rendering process. If you want to set the maximum length of time any one of these unresponsive periods can be, create an integer preference calledcontent.max.tokenizing.time.

Set this to a multiple of content.notify.interval's value, or even the same value higher is probably better. If you set this to something lower than content.notify.interval, the browser may respond more often to user input while pages are being rendered.

If you set a value for content.max.tokenizing.time, you also need to create two more Boolean values -- content.notify.ontimer and content.interrupt.parsing -- and set them both to true.

Control Firefox's response time

If Firefox is opening a page and the user performs some kind of command Firefox will remain more responsive to user input for a period of time. To control how long this interval is, create an integer preference called content.switch.threshold. This is normally three times the value of content.notify.interval, but I usually set it to be the same as that value.

Create the Boolean values content.notify.ontimer and content.interrupt.parsing and set them both to true in conjunction with content.max.tokenizing.time, to makecontent.switch.threshold work correctly.

If you are more inclined to wait for a page to finish loading before attempting to do anything with it you can set content.max.tokenizing.time to a higher value andcontent.switch.threshold to a lower value to allow Firefox to finish rendering a page faster at the expense of processing user commands. In contrast, if you're the kind of person who likes to start reading a page before it's done loading, you can setcontent.max.tokenizing.time to a lower value and content.switch.threshold to a higher one, to give you back that much more responsiveness at the cost of page-rendering speed.

4. Corral close buttons

The integer preference browser.tabs.closeButtons controls how the close buttons (the "X" icons) are rendered on tabs:

0: Display a close button only on the currently active tab.

(You can press Ctrl-F4 to close only the current tab.)

1: Display close buttons on all tabs (default).

2: Don't display any close buttons; the only way to close a tab is by pressing Ctrl-F4.

3: Display one close button at the end of the tab bar.

5. Open search results in a new tab

When browser.search.openintab (a Boolean preference) is set to true, any searches launched from the Search tool bar are opened in a new tab instead of overwriting the contents of the current one. If you launch a new browser window with Ctrl-N and perform a search there, you'll see the search results and the default home page for the new browser instance loading in separate tabs.

Squeeze more tabs into the tab bar

The integer preference browser.tabs.tabMinWidth controls how narrow, in pixels, tabs can be shrunk down before scroll arrows appear on the left and right edges of the tab bar.The default is 100, but you can set this to something smaller so you can fit more tabs in the bar at once. In the same vein, the integer preference browser.tabs.tabClipWidth sets the minimum width, in pixels, that a tab must be in order to show a close button. This is 140 by default, so if you set this to something lower, you'll see more tabs with close buttons when the tab bar is heavily populated.

6. Hack network connections

Proceed with caution! If Firefox's network settings are set too aggressively, they can lead you to being blacklisted for a short time by a given remote server. And you should certainly get permission from the IT department before attempting this kind of hack in a corporate environment. Overall you'll be ahead just "nudging" these settings up a bit. If the values are set very high you won't really get the desired results!

Max out connections to multiple servers

The integer preference network.http.max-connections controls how many simultaneous network connections Firefox will make at any one time to any number of Web servers. By default, this is set to 24, which should work well for most network connections, but you can raise it to 32 and see if that has any effect.

Max connections to the same server

The integer preference network.http.max-connections-per-server controls how many separate connections Firefox makes to the same server, which allows multiple elements in a page to be downloaded in parallel. Normally, this is set to 8, but some people choose to set it as high as 16.

Note, however, that some Web servers will block you if you try to establish more than 8 inbound connections, typically as a bandwidth-protection or antileeching measure -- this is the kind of behavior also exhibited by download managers that try to use as many "slots" as possible to speed things up, and many server admins hate that sort of thing. Also, if you're on a connection that's not fast to begin with (e.g., slow ISDN or dial-up), changing this setting will have no discernible effect, and may in fact slow things down.

Bump up persistent connections per server

Firefox keeps persistent connections to a server "alive" to improve performance: Instead of simply sending the results of one request and then closing, they're held open so that multiple requests can pass back and forth. This means a little less network traffic overall, since a connection to a given server has to be set up only once, instead of once for each separate piece of content; it also means successive connections to the same server go through faster.

The integer preference network.http.max-persistent-connections-per-server controls the number of persistent connections allowed per server. By default, this is set to 2, although some servers will honor a higher number of persistent connections (for instance, if there's a lot of content from their site that loads in parallel, like images or the contents of frames). You probably only want to go as high as 8 with this; more than that may cause a server to temporarily blacklist your IP address depending on how it's configured. (If you're going through a proxy defined by Firefox, use network.http.max-persistent-connections-per-proxy instead of this setting.)

Reduce the interval between persistent connections

If you've already used up all the persistent server connections described in the above setting and Firefox needs to make more connections, the integer settingnetwork.http.request.max-start-delay governs how long to wait before attempting to open new connections. This helps if Firefox's persistent-connection limit has been used up by a number of long downloads, and the browser needs to queue a shorter download on top of that.

Most people set this to 0 (in seconds), with the default being 10. Note that this does not override connection limits imposed by remote hosts, so its usefulness is limited by the whim of the server you're connecting to.

Turn on pipelining

The Boolean preference network.http.pipelining enables an experimental acceleration technique called "pipelining," which speeds up the loading of most Web pages. A browser normally waits for some acknowledgment of a given request from a server before attempting to send another one to that server; pipelining sends multiple requests at once without waiting for responses one at a time.

If you turn this on (that is, set its value to true), also be sure to create or edit the integer preference network.http.pipelining.maxrequests, which controls the maximum number of requests that can be pipelined at once. 16 should do it; some people go as high as 128 but there's not much evidence it'll help. (If you use a proxy, set network.http.proxy.pipeliningto true as well.)

Note that not every Web server honors pipelining requests correctly, which is why this feature is turned off by default and still considered experimental. Some sites may behave strangely if you submit pipelined requests.

7. Stop memory hogging

The default way the Windows version of Firefox consumes memory can be alarming if you don't know what's really going on. People routinely report a memory "footprint" of 75MB to 100MB or more with only a few windows or tabs open, and they assume a memory leak is to blame. While earlier versions of Firefox did have memory leak bugs, they're not the reason for this kind of memory consumption in Firefox 2.x.

Here's what's happening: Firefox caches recently used objects -- Web pages, images -- in memory so that they can be re-rendered on-screen quickly, which drives up memory usage. The following tweaks can make Firefox stake out memory less aggressively. (Note, however, that lightening the memory load might make your pages load a bit more slowly than you're used to.)

Reduce graphics caching

When the Boolean preference browser.cache.memory.enable is enabled (the default), Firefox keeps copies of all graphical elements from the current browsing session in memory for faster rendering. You can set this to false to free up more memory, but pages in your history will reload less quickly when you revisit them.

Another option: Set the value to true and create a new integer preference calledbrowser.cache.memory.capacity. Then specify, in kilobytes, how much memory to set aside for graphics caching. That way you get some of the speed benefits that graphics caching provides without taking a huge memory hit. If you use -1 as the memory value, Firefox will size the memory cache based on how much physical RAM is present.

Reduce Web page caching

Firefox caches several recently visited Web pages in memory so they don't have to be regenerated when you press Back or Forward. The integer settingbrowser.sessionhistory.max_total_viewers determines how many individual Web pages to store in the back/forward cache; each page takes about 4MB (or 4,000KB) of RAM.

By default, however, this value is set to -1, which determines how many pages to cache from the amount of available physical memory; the maximum number of pages stored when you use -1 is 8. Set this value to 0 to disable page caching entirely. That will save some memory, but will also cause Back and Forward navigation to slow down a bit.

Note that this caching is not the same as browser.cache.memory.enable: That setting is for rendering elements on pages like graphics and buttons, and the contents of https-encoded pages, while this setting is for caching the text content of Web pages that have already been rendered or "tokenized."

Swap out to disk memory when minimized (Windows only)

A little-known feature in Firefox allows the Windows memory manager to swap out some of Firefox's physical memory space to disk when Firefox is minimized but not closed. This allows other programs to use the physical memory that Firefox was previously monopolizing.

By default, this feature is turned off, for two reasons: 1) PC memory is generally more plentiful than it used to be, so it makes sense to use it if it's available, and 2) swapping Firefox's memory out to disk will slow the program down when it's restored.

That said, if you run Firefox side by side with other memory-hungry applications, it might help keep them from competing with each other. To enable this feature, create a new Boolean preference called config.trim_on_minimize and set its value to true.