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[@web/dev-server-core] Listening for the unload event throws an error in Chrome #3150
Description
Chrome is deprecating the unload event in a slow percentage-based rollout, so this error will become more prominent with each Chromium release.
Because @web/dev-server-core adds an event listener for unload, this error is thrown:
[Violation] Permissions policy violation: unload is not allowed in this document.
You can reproduce this by enabling the Chrome flag as described here to make it happen every time.
It looks like listening for this event was added recently in #3135, as a way to disable the back/forward cache.
Activity
bashmish commentedon Aug 12, 2026
That's unfortunate, I was hoping to solve it in a simple way, but with this it means we need to handle BFCache.
Resumable WebSocket connection was the issue last time and we'll need to look into how to close it on BFCache event, that's technically possible.
The problem is then that BFCache can also persist other things, so for each finding we might need another fix and another fix. I wanted to disable BFCache completely, but there seems to be no nice way of doing so.
dlockhart commentedon Aug 12, 2026
@bashmish the Chrome developers have been very responsive in this group, so if you describe your scenario to them there they may have some suggestions.