I ran the tests 7 times and then took the median. I'll look into quantifying variance more, but for now here's a boxplot for total on-page CPU time. https://gist.github.com/mattzeunert/de3c8aedd2936a34eeb88b62...

I ran tests on example.com, apple.com, and a WCPO news article (for the ad blocker tests).

The biggest performance issue is that extensions just dump large scripts into pages indiscriminately. Most of the time extensions don't do anything differently based on the content of the page.

I also tested a WCPO news article to see the impact of ad blockers. I picked a local news website specifically because they contain a lot of ads. If a page doesn't have any ads the performance impact of an ad blocker will be slightly negative.

What my tests don't pick up is extensions that only run a certain domains. For example, if you run Honey on a shop they support I expect the CPU consumption to increase a lot more.

I wrote a similar article last year, which tests a few other pages as well: https://www.debugbear.com/blog/measuring-the-performance-imp...

Thanks for the info (and the research in general).

The boxplot looks encouraging (as in, the variance doesn't seem too relevant for drawing conclusions)

I hope to use this as another source whenever marketing wants to add yet another tracker.

How are you installing Firefox extensions in mobile? Is it Android only?

Firefox for Android is (at least for my usage) pretty much desktop Firefox with a touch-friendly UI.

Firefox for iOS is not really Firefox.

All webbrowsers on iOS are basically safari reskinned.

Worth a read “Explanation of the state of uBlock Origin (and other blockers) for Safari” — https://github.com/el1t/uBlock-Safari/issues/158

Correct. Firefox Mobile supports extensions, but only on Android.

Some Chromium based Android browsers do as well.

I use Kiwi Browser on Android, which is Chrome based, and supports extensions.