The source – developers.google.com
On June 26, 2021, a document was added to the Help that parses all the main HTTP status codes in the context of their interpretation by Googlebot. It also describes in detail the impact of network and DNS errors on the representation of sites in the search.
The section on HTTP status codes explains what codes exist and how they affect Google indexing.
- Codes with 2XX status suggest that Google will consider the content for indexing (but there is no guarantee of this).
- The 3XX server response code is associated with a redirect. Googlebot can perform up to 10 clicks along the chain of redirects, then Search Console will show an error in the site indexing report.
- Pages indexed earlier and returning a 4XX code are now removed from the index. URLs that return a 4XX code are not indexed.
- Errors 5XX and 429 temporarily slow down the scanning speed of these pages. This decrease is proportional to the number of individual URLs that return a server error. Indexed URLs that become unavailable and return a server error are removed from Google indexing within a few days. A notification is generated for each error in Search Console.
- Network and DNS errors negatively affect the presence of sites in Search. Googlebot handles connection reset errors, long query execution times, and DNS errors similar to 5XX server response errors.
So far, the document is still only available in English and covers several sections.