Bug 207104 – WKWebView randomly stops loading pages

• Component: WebKit2
• Status: NEW

[Stefan Arentz]

Apologies this is a bit of a vague bug. I will explain what I experience but am definitely asking how to provide better diagnostics.

Steps to reproduce:

In the same tab:

 - Open news.ycombinator.com
 - Open the next link there
 - Go back
 - Open the next link there ...

Repeat for 20 to 30 page. May depend on iOS device - it definitely took more than a dozen pages on an iPhone X with iOS 13.3.

(There is nothing news.ycombinator.com specific here, it is just a handy site to flip through a bunch of random pages)

At one point pages stop loading. They load as blank, or even with the page background color, but no content appears. However you can scroll and (pinch to) zoom and sometimes some content erratically appears and disappears. It is as if the page has become ultra sensitive to zoom/scroll.

The only way to get the tab back to a usable state is to close it and open a new one. Reload does not work. As soon as this happens, the tab is broken with no way out.

Experienced on Safari iOS 13.3 and also Firefox iOS 22. Not just by me, plenty of reports on Twitter.

What kind of diagnostics can I provide?

[Stefan Arentz]

Quick addition: I upgraded to iOS 13.3.1 and the behaviour is the same. I got to link 14 on today’s hackernews at which point the tab in Safari just rendered blank. iPhone X with iOS 13.3.1. Only the Firefox Focus content blockers enabled.

[Stefan Arentz]

Exactly same in Brave browser.

One thing I noticed is that although the page renders blank, the content is tappable. If you randomly hit a link, that page will load. Mostly blank but sometimes with a negative origin so that content begins out of scroll view bounds.

[Radar WebKit Bug Importer]

<rdar://problem/59101877>

[Simon Fraser (smfr)]

When you say "go back", how are you going back? Edge swipe, browser back button?

[Stefan Arentz]

Edge swipe.

[Simon Fraser (smfr)]

I haven't been able to reproduce on iPhone 7 Plus running iOS 13.3 after 30-40 HN links and back. Will try on an iPhone X next (the notch might matter).

[Simon Fraser (smfr)]

Can't reproduce on iPhone XS either.

[Alexey Proskuryakov]

Would you be willing to provide a sysdiagnose, taken right after reproducing this? Please open a new issue at feedbackassistant.apple.com, and then post the feedback id here.

[Simon Fraser (smfr)]

Also a video recording of you reproducing would be useful. I tried for about 20 minutes and failed.

[Stefan Arentz]

Created attachment 392076 [details]
Not completely how this bug started but symptoms are the same I think.

[Stefan Arentz]

After upgrading to iOS 13.3.1 I am having a hard time reproducing this with the STR in the first comment. However, it is still happening to me during regular browsing.

Exact same thing where the page loads blank, content seems to be there but not rendered. Scroll and pinch to zoom sometimes makes the content appear. The tab is not usable anymore from there on.

Another thing that I noticed while going through pages from HN rapidly is that sometimes after going back to HN, the page briefly flashes back to the page I was just looking at. That is definitely something new that I had not noticed before.

I'll work on capturing some logs next.

[Stefan Arentz]

Created attachment 392094 [details]
Another case

[Stefan Arentz]

Added another video of a case that happens during casual browsing. HN still renders fine but I assume that is because the page is cached.