404 or 410 Status Codes Will Not Impact a Website’s Rankings
If Google identifies 404 or 410 pages on a site, it will continue to crawl these pages in case anything changes, but will begin to phase out the crawling frequency to concentrate more on the pages which return 200 status codes.
Google Checks Status Code Pages Before Attempting to Render
Google checks the status code of a page before doing anything else, such as rendering content. This helps to identify which pages can be indexed and which pages it shouldn’t render. For example, if your page returns a 404, Google won’t render anything from it.
Google Does Not Index 404 Pages
If a page returns a 404 error code, Google will not index the page’s content. However, if the page has recently become a 404 page and Google has not crawled the page to see this, the page will still appear in search results. This error could also occur if the server displays a 404 page, but the code shown to crawlers is still a 200 status.
Signals Are Kept For 4xx or 5xx Error Pages Previously Dropped from the Index When They Are Re-added
If your pages displayed a 4xx or 5xx error for a while and were dropped from the index but become available again after a month or so, for example, Google will be able to return them to the search results in the same state they were before. They won’t have to start trying to rank from nothing.
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.