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Summary:

Firefox 4 included an update to its JavaScript engine which made serious performance gains. Now Mozilla is addressing another cause of sluggishness: slow start-up times caused by add-ons. It’s published a list of the worst performers, and is recommending that users disable add-ons they don’t use.

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Firefox 4 included an update to its JavaScript engine, which made for some serious performance gains. Now Mozilla is going after another cause of sluggishness: slow start-up times caused by add-ons. If your install of Firefox feels slow to start up, you may want to try disabling some add-ons. According to Mozilla, on average, each add-on a user has installed adds 10 percent to Firefox’s start-up time. But that’s only for the average extension; some add-ons have a much worse start-up time impact than others.

To encourage add-on developers to consider this performance hit and optimize their add-ons, Mozilla has started testing the 100 most popular Firefox add-ons and releasing a weekly-updated list of their impact on browser start-up time. Here is a “rogue’s gallery” of the 10 add-ons with the worst impact on start-up time:

  1. FoxLingo – Translator / Dictionary
  2. Firebug
  3. AniWeather
  4. FlashGot
  5. FoxClocks
  6. FoxyTunes
  7. Video DownloadHelper
  8. FastestFox – Browse Faster
  9. Xmarks Sync
  10. SimilarWeb – Find the Best Sites on the Internet

The two worst-performing add-ons in the list, FoxLingo and Firebug, add a whopping 76 percent each to Firefox’s start-up time.

As well as publishing the slow add-ons list, Mozilla will also be adding warnings to the Add-On Gallery listing of any add-on that slows Firefox’s start-up time by 25 percent or more. The Mozilla effort to improve add-on performance is not just about “naming and shaming” poor performing add-ons, though,  Mozilla is also providing assistance to developers to optimize add-ons by updating its performance best practices documentation, and by releasing tools to help developers test their products.

The availability of a wide range of useful extensions is one of the reasons I use Firefox; I compiled a list of my favorites here. But Mozilla’s testing data shows that it’s good idea to regularly review the add-ons you have installed and disable those you no longer or rarely use, particularly if they appear on the list of the worst offenders above. Disabling an add-on stops Firefox from loading it, so it will no longer affect start-up time, but keeps the add-on in your add-on manager list so it can be re-enabled when you need it. Firebug, for example, is a really useful debugging tool, but I only use it very occasionally, so from now on I’m going to keep it disabled.

Photo courtesy Flickr user Photo Monkey

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  1. Vince Verbeke Tuesday, April 5, 2011

    I’ve noticed this as well. Just disabled the Qualys BrowserCheck Plugin. My FF is now much happier. Thanks for the article.

    1. Glad to help, Vince.

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