I have a simple web page that does an xhr (post) call every 5 seconds to an endpoint to fetch information and update the page. It was understood that mobile browsers usually throttle queued actions (setTimeout, setInterval) when the tab is no longer active. But the execution used to restart when the tab again became active. However, on iOS 18’s Safari, something has changed. The execution of setTimeout scripts do not continue immediately after the tab becomes active, at times it takes 40 seconds for the actions to resume and at other times it takes 120-150 seconds. I could not find anything in the Safari change log that alludes to this change. This is specifically occurring on iPhones.

Has anyone else noticed this?