Chrome on Android already heavily throttles (or outright kills) background tabs, but Chrome on the desktop has mostly allowed inactive tabs to do whatever they want. Unfortunately, having several tabs open using performance-intensive JavaScript code, like timers, can cause Chrome performance and battery life (if you're on a laptop or other portable device) to suffer.

Google originally planned to start throttling background tabs in Chrome 56, but due to some concerns it would break a large amount of web pages, it was put off. Now the feature has finally arrived, as part of Chrome 57.

Here's how it works: every background tab has a time budget, in seconds, for running timers. The time budget goes into effect after the tab is in the background for 10 seconds. When a timer runs, the run time is subtracted from the budget. The time budget continuously regenerates, currently at a rate of 0.01 seconds per second, but that may be adjusted in future releases.

To prevent many pages from breaking, there are a few exceptions to this rule. Any tabs playing audio or containing real-time connections (like WebRTC and WebSockets) are not throttled. Google says that throttling leads to about 25% fewer busy background tabs, which obviously translates to better battery life on laptops.

To try this out, simply update Chrome on your computer or Android device to Chrome 57.