Mozilla fixes 14-year old Firefox bug, turbocharges Adblock Plus

Last year, Mozilla published a blog post in which it noted that popular ad-on Adblock Plus could, under certain circumstances, drastically increase memory usage in Firefox. The problem was related to how Firefox handled ABP’s style sheets and could, in certain edge cases, send memory usage rocketing up to 2GB. While not necessarily a problem for relatively high-end systems, plenty of midrange computers get grumpy if a process sucks down that much RAM — and applications that use that much memory also have a tendency to bog down in general. Firefox 41, released yesterday, solves this problem, with impressive results.

Firefox doesn’t seem to have explicitly called out the improvement in its version 41 patch notes, but the team at ABP noted the difference in their own writeup of the new release. I don’t normally use AdblockPlus on Firefox, but I decided to take the new version out for a spin on this test site. If you’re still on a pre-41 version of FF and you use ADP, you’ll see RAM usage explode on that test page — my browser topped out around 1.89GB. After an update to FF41, the same page tops out around 500MB — and keep in mind, that’s a custom worst-case scenario for this style sheet bug.

Memory usage on Firefox should now be roughly similar whether you use Adblock Plus or not. There’s no word on whether or not it will impact some of the other popular adblocking clients, some of which were designed to get around ABP’s high memory use in Mozilla’s browser in the first place. According to VentureBeat, the new release contains a number of other improvements, including instant messaging as part of Firefox Hello, improved box-shadow rendering, and a range of additional developer-side improvements.

Web brower market share. Image courtesy of Wikipedia

Whether this will do anything to fix Firefox’s long-term browser share decline is another question. Different tracking standards count browser share differently, but most reports agree — Firefox is long past its peak usage and has surrendered a great deal of its market position to Google Chrome. Microsoft clearly hopes that Windows 10 and its nascent Edge browser will reverse that trend. Given that Windows 10 goes to great lengths to set its new browser as the default option for end-users, we expect to see some movement in Microsoft’s direction in the long-term, though how long that persists is still an open question. End users are often comfortable installing their own browsers, and that could work against any attempt Microsoft makes to regain lost market share. Firefox, meanwhile, needs to keep working on reducing its reputation as a memory hog.