Sometime in early June 2021 some SEOs and webmasters began noticing a spoke in soft 404s reported in Google Search Console. I’ve seen the topic come up a bunch of times in the forums but it was not as super widespread as the soft 404 errors from April of this year.

John Mueller said in this morning’s video that Google has changed how it handles soft 404 detection saying it looks at desktop vs mobile differently but in Search Console only reports what it shows in mobile and not on desktop. So if Google sees your mobile site showing a soft 404 for a specific page, it will label it as such but the desktop site might still show up in the search results for that page. John said this is new and kind of surprised him when he heard it. John said this started sometime about a month ago and they are using examples on how to improve the classifer for soft 404s. He said this at the 21:26 mark in this video:

That being said, there may be an issue with the sensitivity controls Google uses for detecting soft 404s. Again, soft 404 are when Google thinks your page that returns a 200 OK status code should in reality return a 404 page not found status code. A lot of sites serve 200 codes for pages that should return 404s, so Google handles it with soft 404s and reports to you which pages are labeled as such in Search Console.

In any event, there has been a number of complaints in numerous Google Webmaster Help forums over the past few weeks or so with this. Tom Rothwell wrote:

He shared this chart:

Mark Sprenger wrote:

Now, John Mueller of Google was asked about this in a previous Google hangout from the other week at the 18:14 mark into this video where someone asked “Did Google change something with the soft 404 detection?” John Mueller from Google responded “probably.” He then said:

Here is the video embed:

Also this morning, it was in another hangout with John at the 21:26 mark where John goes into why mobile vs desktop pages may show different soft 404 statuses. It is interesting to listen to. He said he looked into this issue with one of the sites that posted details in the forum and he said it turned out that Google has a system that tries to recognize soft 404s across desktop and mobile separately. John said sometimes Google detects soft 404s different for the same page on desktop vs mobile and that is why you would see differences between device type. So Google can have different soft 404 statuses across your mobile vs desktop URL. So if you have more examples of this, share them with John so they can improve the classifiers.

Here is the transcript from this morning’s video:

So if you have examples, maybe add it to one of the threads above and maybe Google can debug it on their end?

Forum discussion at <a href="Google Webmaster Help forums.

Update: John Mueller made some clarifications on Twitter: