Bug 219102 – [iOS] beforeunload event does not fire in MobileSafari

• Component: DOM
• Status: REOPENED

[Chris Dumez]

beforeunload event does not fire in MobileSafari on iOS. This is inconsistent with the HTML specification and with Safari on macOS. It is therefore confusing for Web developers that this event does not fire.

[Chris Dumez]

<rdar://problem/70550655>

[Chris Dumez]

Created attachment 414464 [details]
Patch

[Geoffrey Garen]

Comment on attachment 414464 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=414464&action=review

r=me

> Source/WebCore/ChangeLog:9
> +        MobileSafari on iOS does implement WKUIDelegate's runJavaScriptAlertPanelWithMessage because

does not

> Source/WebCore/ChangeLog:16
> +

Might be worth mentioning that iOS already fires the unload event, so running an event at this time is not a significant change in policy.

[Chris Dumez]

Created attachment 414466 [details]
Patch

[Chris Dumez]

Created attachment 414470 [details]
Patch

[EWS]

Committed r269983: <https://trac.webkit.org/changeset/269983>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 414470 [details].

[Chris Dumez]

Reverted r269983 for reason:

Seems to have regressed PLT5

Committed r270560: <https://trac.webkit.org/changeset/270560>

[Srinivas]

I have observed that the beforeunload event is not firing in iOS Safari again, similar to the previous issue reported (Bug 219102). This issue persists on iOS 17 and can be reproduced by navigating away from a webpage with a beforeunload handler. It works fine on macOS Safari. Please investigate this recurring problem

[Darin Adler]

Yea that’s expected. We have not yet successfully fixed this bug.

[Srinivas]

It was working before we update iOS 17. Not sure if it was broken as part of iOS 17 changes.

[Darin Adler]

That is surprising since the history above says we didn’t fix it!

[Mark]

+1 on this issue.

I'm seeing `beforeunload` not getting triggered on iOS 17 and iOS 18 on page refresh. Is this expected?

Demonstration: https://drive.google.com/file/d/1MNp1_HmZQR_2YnRnlOQinKq-RMMOAfOQ/view?usp=sharing
Doesn't seem documented in the [docs](https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event)

[Darin Adler]

Yes, it’s expected. Nobody has fixed this bug yet. The attempt back in 2020 was unsuccessful.

[Mark]

Thanks Darin! Is it being actively worked on or not in your plans?

If not, what's the alternative here? Can we use `unload` despite advised against it?

All we need to do is to close a pop-up on page refresh. This is because if we don't, post-refresh, we can't open a new pop-up on WebKit mobile.

[Darin Adler]

I don’t know the answers to those questions

Is there any estimate for when this will be fixed? This has been here for over 4 years now and it is a major pain point.

[Martin (MConverter)]

This bug is negatively impacting the UX of our web app for iPhone and iPad users. As others have said, having this issue for years is a major pain point.