The desktop versions of Chrome — including the Mac edition — now throttle the performance of background tabs, according to Google, reducing CPU demand and hence the browser's power consumption on MacBooks.
In particular the Chrome 57 update limits the timer fire rate of background tabs deemed to be consuming too much power, the official Chromium blog explains. The tactic is intended to limit average CPU load to 1 percent of a core.
The change should result in 25 percent fewer "busy" background tabs. Crucially, tabs with audio or real-time connections are immune to throttling.
Google notes that through a later update, Chrome will eventually be able to suspend background tabs completely. New APIs will handle tasks that need to continue operating.
The Mac version of Chrome has often faced criticism for being CPU- and RAM-intensive. The browser took a significant step forward with Chrome 55, which drastically improved memory usage.