Why Are Chrome Background Tab Timeouts and Intervals Slower?

Background Tab Timeouts and Intervals in Chrome

In testing the precision of setTimeout in Chrome, a discrepancy was observed when running the test in a background tab. It was noticed that the timeouts and intervals executed significantly slower compared to when the tab had focus. This behavior was not seen in Firefox or Internet Explorer.

This observation suggests that Chrome either suspends or slows down JavaScript execution in tabs that lack focus. As a result, background tasks such as periodic server checks using XHR and setInterval calls may not function as intended.

The underlying code change responsible for this behavior has been identified. When a tab is inactive, the JavaScript function is invoked a maximum of once per second, ensuring resource optimization.

While this timeout and interval suspension can be seen as a performance enhancement, it also limits the functionality of background tasks. One workaround involves using Web Workers, which provide a separate thread for continuous execution, even in background tabs.

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