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"With the visibility API, you can gracefully pause or degrade the timer to a much longer poll when the tab is in the background."

Note that this is already enforced for setInterval in some browsers -- I think Chrome changes the minimum interval to 1000ms from 4ms when the tab is in the background.

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Ah, interesting -- is this documented anywhere? I did see mentions of Chrome downgrading background tabs, but did not find any specific numbers.

I mentioned it quickly on twitter: https://twitter.com/#!/ChromiumDev/status/76634744607096832

And updated the MDC docs on it: https://developer.mozilla.org/en/DOM/window.setTimeout#Minim...

I'll get it added to www.chromestatus.com now.

Here's the corresponding bit for Mozilla:

https://bugzilla.mozilla.org/show_bug.cgi?id=633421

I definitely experienced the same in Chromium.

Once upon a time, I also experienced similar timing weirdness on inactive tabs with .gif animations for some version of Chromium (tab out, wait a few seconds, tab back and suddenly the animation is superfast for a few seconds) but I can't reproduce it with modern versions.

Update: Here's the Chromium one: http://codereview.chromium.org/6577021

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