Firefox 61 introduces a number of small but notable changes to the engine that should increase its general speed. Perhaps the most obvious is the changes Mozilla has made to tab switching, called ‘tab warming’. Essentially, the browser will premptively begin to load tabs as you hover over them, rendering some of the page before you switch. For users, this gives the illusion that things are loading snappier.
Fewer Frame Drops
It’s joined by a feature called ‘retained display lists’ which should improve the smoothness of general browsing. For the unfamiliar, the display list is a database of all the elements that will be drawn on the page, from highest to lowest. “Historically, the entire display list was computed prior to every new paint. This meant that if a 60fps animation was running, the display list would be computed 60 times a second,” explained Firefox HTML 5 engineer Potch. “For complex pages, this gets to be costly and can lead to reduced script execution budget and, in severe cases, dropped frames. Firefox 61 enables ‘retained’ display lists, which, as the name would suggest, are retained from paint to paint. If only a small amount of the page has changed, the renderer may only have to recompute a small portion of the display list.” The result is a close to 40% reduction in dropped frames, which may not be too noticeable for the end user, but should pay off in all kinds of ways. The other main features are targeted at developers, rather than regular users, with a new ‘accessibility inspector’. As you would expect, it lets you see how the browser will show information to people with accessibility issues, letting you tweak your website to better fit their needs. Its joined by a number of other, smaller developer tools, which you can find more information about on the official blog. Meanwhile, Mozilla is rolling out its Monitor tool to 250,000 users to tell them when their passwords have been comprimized. It’s dedication to thinking outside the box is starting to pay off, though it’s still far behind on battery life.
