The icon that displays on my iPhone XS (Safari) is incorrect. If I bookmark the site or add to favourites the new/correct image is displayed but if I click the 'tab' icon, where you see all open tabs it's a very old favicon.
The image that is displayed isn't my the hosting. I've even changed hosting provider recently so everything is fresh. I can only assume the previous icon is cached from the old site on my phone - but the same domain name.
I have cleared Safari's cache and in "Advanced" the "Website Data" but no matter what I do the icon won't change. I've tried adding ?v=2 to the URL to try and force a fresh download but no matter what, it won't display the image I'm specifying in the head.
I load my icons like this:
<link rel="apple-touch-icon" href="icon.png" sizes="192x192">
<link rel="shortcut icon" href="favicon.png" sizes="32x32">
Any ideas? The only thing I can think of is the device itself is storing aspects on websites but outside of Safari and the cache?
Interesting, with further research I found out it's a known issue for Safari iOS/iPadOS to cache favicons in a hidden location.
Safari has extremely aggressive favicon cache. I've seen it happen multiple times on large production websites that the favicon doesn't update for months.
It seems like macOS has a folder that stores that data, but unfortunately that location is not accessible via mobile (to my knowledge).
Without giving you a fix for you issue, I hope that my answer might bring light on this cache issue, as I'm experiencing the same problem on my iPhone 13 Pro 15.6.1.