Google estimates that background tabs account for as much as a third of Chrome’s power usage. Chrome 57, which became available this week, is limiting this power drain by throttling background tabs that consume too much power. The consequences of throttling background tabs will not be the same for all websites. Social media and news sites tend to make heavy use of JavaScript timers and these sites will see the greatest effects. Background tabs that are playing audio or which use real-time, client-server connections like WebSockets and WebRTC will not be throttled.

Source: Forbes March 15, 2017 18:45 UTC