For several months, some Google cache links on search results pages have been serving 404 page not found errors when people clicked. While Google confirmed that this mobile-first indexing cache bug didn’t affect the site’s ranking, that didn’t stop webmasters from being concerned.
Cached page: Unfortunately, it looks like we’re currently still not showing a cached page for many mobile-first indexed sites. This is a bug, not by design, and should get resolved over time. It’s just the UI, it doesn’t affect crawling, indexing, or ranking.
— Google Webmasters (@googlewmc) June 14, 2018
Google fixed the bug: This weekend, Google rolled out a fix that has resolved the issue that was causing the cache link to serve a 404 page.
Google has not yet confirmed that they fixed it fully but, based on all of my tests, the issue is certainly not as widespread as it once was.
What was the bug? You were simply unable to view the cached version of your web page from the Google search results. There was a hack, but that is no longer needed. Here is a screenshot of the error that people were seeing:
Why did it matter? The truth is, it didn’t matter much. It caused concern amongst SEOs and site owners that the cache link would 404. But Google said it didn’t impact rankings or anything else; it was just an internal bug.