[matsemann]

The point is to play nice. "I have this task the page needs to do, but I can wait a bit until more convenient". Not "browser is idle, let's mine some bitcoin" as you suggest.

[nottorp]

Actually I wasn't thinking of bitcoin, but for example of needless auto refreshes and animations.

Seriously, web devs need to learn to respect my battery and electricity bill more.

[neweroldguy]

This is just a generic “old man shouting at clouds” complaint at this point. You’re not engaging with the material at all.

[Kiro]

This does not do what you think it does. You're tilting at windmills.

It's not about doing stuff in a tab that isn't in focus. "Idle" refers to the main thread idling in the page you're currently using, so it's about controlling the execution order and priority of JS tasks. E.g. on Google Maps you give priority to rendering the visible map tiles while deferring preloading the surrounding non-visible tiles until the main thread is unblocked (and thus idling).