api.BeforeUnloadEvent - unsupported on iOS due to a bug

[marto55555]

What type of issue is this?

Incorrect support data (example: BrowserX says "86" but support was added in "40")

What information was incorrect, unhelpful, or incomplete?

The beforeunload event is unsupported on iOS and iPad due to a bug: https://bugs.webkit.org/show_bug.cgi?id=219102

What browsers does this problem apply to, if applicable?

Safari

What did you expect to see?

The beforeunload event should work and prevent automatic navigation to a different website, etc.

Did you test this? If so, how?

Yes, tested on an iPhone with iOS 18.

Can you link to any release notes, bugs, pull requests, or MDN pages related to this?

Related bug: https://bugs.webkit.org/show_bug.cgi?id=219102

Do you have anything more you want to share?

No response

MDN URL

https://developer.mozilla.org/en-US/docs/Web/API/BeforeUnloadEvent

MDN metadata

MDN page report details

• Query: api.BeforeUnloadEvent
• Report started: 2025-07-31T13:00:52.147Z

[Josh-Cena]

BeforeUnloadEvent and beforeunload event are not the same thing, just like PointerEvent and click event are not the same thing. You will find Safari correctly lacking support on https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event#browser_compatibility.