Google says it will limit the amount of processing power that background tabs can consume in Chrome. The change is designed to increase battery life on mobile devices without affecting usability too much.
It builds upon an existing policy that means any background tab can only carry out actions (such as reloading data) once a second. With this in place, the browser batches together actions across all the background tabs to reduce the overall load on the processor.
The new policy means that once a tab has been in the background for 10 seconds it will have an individual time “budget” on running actions. Any actions eat into this budget, while during this period of inactivity the budget is regenerated by 0.01 seconds for every one second that passes. The tab can’t carry out any actions when the budget is at or below zero.
The idea is to set and manage the budget (including automatically tweaking the regeneration rate) so that no background tab is ever averaging more than one percent use of a processor core.
There’ll be exceptions for audio (including a few seconds’ grace to allow for the silence between tracks) and applications that use real-time connections such as WebSockets and WebRTC, which are used for functions such as chat tools.
In the long run Google wants to be able to completely suspend all background tabs, but concedes it can’t do that until most developers have stopped relying on them. It’s set a goal of 2020 to reach this point.