Before complaining about Firefox for high memory usage, make sure the Adblock Plus extension is installed, says Mozilla. Using the popular Adblock Plus add-on to block ads in Firefox browser and feeling that it not only blocks ads but also helps pages load quickly in the browser, you are wrong. Mozilla’s claims that, in fact, Adblock Plus is greatly increasing the memory used by Firefox, this is a surprise.
Second, “there is a overhead of about 4 MiB per iframe, which is mainly due to the ABP injecting a giant stylesheet into each iframe. Many pages have multiple iframes, so this can add up quickly”
ABP developer Wladimir Palant responds to the first saying “Regarding general memory usage (JS objects), should help here. This will allow us to use typed arrays for data storage that will be much more efficient.”
And for the second one, Stylesheet one, he says, “Regarding this stylesheet – we have two projects running that might end up reducing the number of filters eventually, but other than that, I don’t think we can do much about this”
Palant further explains “the purpose of this style sheet is to hide things that cannot be locked – a feature called element hiding. As far as Adblock Plus is concerned, only one style sheet is created and registered globally. There is a rule for each element hiding filter meaning about 20k now if you’re using EasyList. The fact that Firefox internally creates a separate (and not exactly small) stylesheet for each frame is something I just learned from https://bugzilla.mozilla.org/show_bug.cgi?id=988266.”
Nicholas from Mozilla concludes: it’s good that the add-on blocks ads, so you can allow it to use the extra memory, but if you’re using a PC with a low configuration, you might have different priorities. He expresses the hope of working with the authors of the ABP to resolve this, “if you hear people complaining about Firefox’s memory usage, one of the first questions to ask is whether they have the ABP installed.”
So what do you say now, Adblock Plus user?