The best thing about Firefox is that it’s incredibly customizable, but have you ever wondered how much of a price all those add-ons take? Here’s how to see which add-ons slow down Firefox startup time the most.

Thanks to @codinghorror for pointing it out on Twitter, we can now know for sure, thanks to Mozilla Add-ons list of slow-performing extensions during startup—this doesn’t mean they necessarily slow Firefox down once it’s loaded, of course.

The fun part is that #8 on the list is the FastestFox extension, which is supposed to make Firefox faster. Instead, it seems to slow down the startup by 33%, though it’s not the only popular extension to make the browser slower—Xmarks, Adblock, NoScript, and Greasemonkey all slow the startup down as well. If you’ve combined them all together, you’re looking at much slower startup speeds.


Head over to the list, and see if your favorite add-on is slowing Firefox startup down for you.

Firefox Add-ons with the Slowest Start-up