Soft 404s Cannot Be Passed to Other Pages via Redirects or Canonicals
A soft 404 cannot be passed on to another page via a canonical or redirect. Google ignores the content on a page if it detects that it is a 404 or soft 404.
Many-to-one Redirects & Noindexed Pages Are Sometimes Treated as Soft 404s
Noindexed pages and too many pages that redirect to one URL can both be treated as soft 404 errors by Google. Having soft 404s doesn’t impact the perceived quality of your website, but these pages won’t be crawled as frequently or indexed at all.
Image URLs Can be Flagged as Soft 404s in GSC
The GSC Index Coverage report may flag image URLs as soft 404s if they have a non-standard image URL. This is because they are seen as a 200 page without any HTML.
Redirected URLs Can Appear as Soft 404s if Many Pages Are Redirecting to One
Redirecting URLs shouldn’t be showing up as soft 404 errors unless you’ve removed a lot of pages and are redirecting them all to one page.
Use the URL Removal Tool & Sitemaps to Inform Google About Removed Pages
The URL Removal tool can be used to remove entire subdirectories from Google’s index usually within a day. When removing groups of URLs that don’t fall under one subdirectory you can make them 404s and tell Google they’ve changed recently via a sitemap file.
Noindex & 410 Pages Are Removed Faster Than 404
Noindex and 410 remove pages from Google’s index at about the same speed, and both are slightly quicker than using a 404.
410 May Remove Page From Index Faster Than 404
In the mid and long term, a 404 error is the same as a 410 because they will both be dropped from the index and crawling is less frequent. However, a 410 may cause a page to fall out of the index a little bit faster than a 404 by a couple of days or so.
Sitemap Files Returning 404s Don’t Cause Issues for Google
Sitemap files that return 404s don’t cause any issues for Google from an SEO perspective, they will just be left as 404s.
Google Sometimes Wrongly Identify Soft 404s
Examples of a soft 404 can include redirects to a shared page, or a page with a 200 response code that has no indexable content. However, Google sometimes wrongly identifies soft 404s, like on development sites talking about 404 pages, which can be mistaken for the page not being found.