Skill Level: Medium
Firefox 7 is a great new version of the popular web browser, with improved memory management and quicker startup times – if you followed our advice on how to install FF7 to benefit from startup speed improvements… We have already discussed how to change the layout of Firefox (since the new look of Firefox 4 onwards) but what about tweaking Firefox 7 to make it even quicker?
There are several guides around the internet but many are years old or just plain wrong so it is time for an updated guide. In particular, Firefox 6 (and therefore Firefox 7 too) made changes ‘under the hood’ which render some previous tweaks for versions 4 and 5 redundant or even undesirable.
Initial Steps
- Before tweaking, check for any add-ons that you no longer use or could do without – the more you have installed the slower and less stable Firefox will become:
In the Firefox menu bar click Tools then Add-ons to open the Add-ons Manager. Now click on Extensions and if you no longer need an extension then remove it or at least disable it. Restart Firefox when you have finished.
- All the following tweaks are done by changing or adding values to the Firefox configuration page known as about:config. To be on the safe side, you should make a note of the ‘before’ and ‘after’ values of each tweak and (highly recommended) backup the Firefox preferences file that contains all the configuration options in case you want to revert back to your original settings:
The configuration file is called prefs.js and can be found in the following place in your operating system drive (usually C: drive):
\Documents and Settings\<username>\Application Data\Mozilla\Firefox\Profiles\<profile ID>.default\ in Windows XP or
\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile ID>.default\ in Vista and Windows 7.
You may need to show hidden files to view these folders. Copy the prefs.js file to another location on your hard drive whilst Firefox is closed – you could then copy it back (whilst Firefox is closed, replacing the problematic version) if you encounter any problems with Firefox after applying these tweaks.
Tweaking Firefox 7
Open Firefox and type about:config in the address bar and press Enter. Click the box warning “I’ll be careful I Promise” to reveal a long list of preferences used in Firefox.
- To change a preference which is an integer (number) or a string (text) you need to double click on the preference name and you will be prompted for the new value. If you double click on an entry that has a Boolean (true or false) value, the entry will switch from true to false or vice versa – double clicking again will revert it to its original value.
- To add a preference (if the preference name is not already listed in your about:config page) you need to right click on an empty space in the about:config window and choose New followed by String, Integer or Boolean depending whether the value of the preference is text (String), a number (Integer) or true/false (Boolean).
Tip: You can scroll down the list of preferences to find the right one but the quickest way is to type part of the preference name into the Filter bar at the top of the config page – it automatically reduces the list to show only those preference names that include the text you typed.
Changing Preferences
Change the following preferences to the new values shown. If the preference is already set to this value then skip it and move on the next. If the preference does not exist then you need to add it:
browser.display.show_image_placeholders: false
Stops the display of placeholders while images are loading to speed up the page. Default is True
content.notify.backoffcount: 5
Sets the maximum number of times the content will do timer-based reflows to 5. After this, the page will only reflow once it is finished downloading. This is a new integer value. Default is -1 (no limit)
content.notify.interval: 120000
Sets the minimum amount of time to wait between periodic reflowing of the page to 0.12 seconds – stops Firefox becoming slow by reflowing too frequently. This is a new integer value. Default is 120000
content.max.tokenizing.time: 360000
Sets the maximum amount of time Firefox will be unresponsive while rendering pages – set to 3 times the content.notify.interval above. This is a new integer value. Default is 360000
content.notify.ontimer: true
Ensures Firefox does not reflow pages at an interval any higher than that specified by content.notify.interval above. This is a new Boolean value. Default is True
content.interrupt.parsing: true
Sets Firefox to interrupt parsing a page to respond to UI (user interface) events to prevent it becoming unresponsive until parsing is complete. This is a new Boolean value. Default is True
content.switch.threshold: 750000
Sets the number of microseconds of inactivity that puts Firefox into low frequency interrupt mode. This is a new integer value. Default is 750000
network.prefetch-next: false
Stops Firefox automatically prefetching (loading) the contents of pages linked to by the page you are viewing – in most cases you will never visit those links so this time is wasted and it is a security risk because you are unwittingly downloading (possible virus/adult) content only linked to by the current page but which you have not chosen to load. Default is True
network.http.max-persistent-connections-per-server: 8
Increases the maximum number of persistent connections per server which can help speed up loading of multimedia rich sites. Default is 6
network.http.pipelining: true
Can send multiple requests to a server together in order to speed up loading of webpages. This is not supported by ALL servers – some servers may even behave incorrectly if they receive pipelined requests. Default is False
network.http.pipelining.maxrequests: 8
Sets a maximum number of multiple requests that can be pipelined to prevent overloading the server. Higher values will cause a delay before the first request completes but will make the last request complete sooner. Higher values will also cause more of a delay if a connection fails. The maximum value is 8. Default is 4
network.dns.disableIPv6: true
Disables IPv6 DNS lookups to prevent a significant delay with poorly configured IPv6 servers. Default is False
browser.tabs.animate: false
Disables all tab animation features (e.g. when you click the ‘New Tab’ (+) button) to make the tab interface feel quicker. Default is True
Finally, if you want Google searches in the address bar to search by name and go straight to the right website (e.g. NewYorkTimes would go straight to the nytimes.com website) rather than just perform a standard Google search:
keyword.url: http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=1&q=
(Note: this is for google.com – you may want to change it to your own country version e.g. for UK just replace the google.com bit with google.co.uk)
Now close Firefox and reopen it to apply all the tweaks and you should find Firefox is quicker and more responsive 
Personalizing The Tweaks
The above tweaks have been tailored for Firefox 7 specifically and have improved speed in our own tests – but your mileage may vary depending on your exact network configuration, sites visited and other software installed. One of the best things about Firefox is the variety of add-ons available – it is also one of the worst as it means there is an endless variety of possible Firefox 7 configurations…
In particular the 5 ‘network.’ preferences may not be a ‘one size fits all’ solution for you – you may need to experiment to achieve the best settings for your particular implementation of Firefox e.g. by changing them one at a time to different values or back to the default settings. We have provided the Firefox 7 defaults for you in case you wish to revert to them.
Still Having Speed Or Crashing Problems?
If you have always let Firefox upgrade itself over the years (from version 2 or 3 onwards) or you have played with loads of extensions and now find Firefox slow or unresponsive, you should seriously consider making a fresh start with a new Firefox installation – we’ll show you how in our article reinstalling Firefox from scratch to fix speed and stability issues.
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i had to experiment a bit with these and backed off someof the network ones but has made a difference overall