Google Explores Chrome JavaScript Throttling To Add Hours Of Battery

Chrome tabs AH 2019 rescale 2020

Google is reportedly experimenting with new features in Chrome, tacking in JavaScript throttling as a way to improve battery life. That's based on a feature discovered in the latest test builds for Chrome 86 for Windows, Mac, Linux, Android, and Chrome OS.

The underlying change being instituted is fairly straightforward. Google's experiment works to limit what JavaScript does when pages are pushed to the background. As Chrome currently stands, the browser checks, for instance, whether or not a page is scrolling or whether or not a user is interacting with ads.

Those types of activity are really unnecessary when users have moved to a different tab in Chrome. At least a few of those completely unnecessary tasks appear to bring a significant battery drain to end-users. So Google is looking to limit when JavaScript wakes up to perform those actions on background pages. And the results of that, as reported are promising.


What does throttling JavaScript do for battery life?

Now, as Google's own tests show, the battery savings available by throttling JavaScript wakeups doesn't make it better on that front than Apple's Safari browser. In fact, it still falls short by as much as an hour of overall battery life in some cases. For instance, Google's test shows that Chrome, with throttling down to one wakeup per minute, runs for 1.1-hours less than Safari.

There's no information as to the size of the battery or what device is being tested on. And that's a significant difference. But it's no less than '1.8' hours longer than Chrome typically lasted in the test without throttling battery-intensive JavaScript tasks.

The overall results are, of course, subjective beyond the device and battery size in question too. For tests with YouTube running in the foreground and 36 background tabs, the company notes 13-percent in savings. Or around 36-minutes. So there may also be some direct correlation to the number of tabs open too.


There's certainly dependence on what, exactly, users are running in the foreground, though. With a blank foreground tab, the improvement is closer to two hours.

Chrome is looking to compete where it matters with battery and memory savings in under a month's time

Now, Google obviously has its work cut out with this feature. It's going to need to weigh the cost-benefit of gaining new users or retaining those with cutting away at how much activity background tabs can engage in. And it may take some time for the company to optimize the changes so that they're ready for the Stable Channel. It will almost undoubtedly become even more efficient moving in the interim.

At the very least, this won't arrive until Chrome 86 does. That's currently slated for the first week of October — or the second week for Chrome OS.


In the meantime, Google has also been working on memory-saving features with Microsoft. So this appears to be part of a broader test to instantiate improvements that will make the software more competitive. As that other test stands, at last reporting, it was saving as much as 200MB of memory at a rate of around 27-percent.

With both memory and battery savings in place, it should be fairly easy for the world's most popular browser to maintain that position.