Google has published a guide detailing how various status and error codes affect Google Search.
It’s a useful reference document you can keep to hand and consult if you’re wondering about the impact of the various status codes and errors. It covers the 20 top status codes that Googlebot encountered on the web, as well as the most prominent network and DNS errors.
The guide is broken down into:
HTTP status codes:
- 2xx (success)
- 3xx (redirects)
- 4xx (client errors)
- 5xx (server errors)
Network and DNS errors
Google notes the following:
- An HTTP 2xx status code (success) is not a guarantee of indexing
- Googlebot follows up to 10 redirect hops. If the crawler doesn't receive content within 10 hops, Search Console will show a redirect error in the Index Coverage report.
- A 301 sends a strong signal, whereas a 302 or 303 sends a weak signal, that the redirect target should be canonical.
Network and DNS errors have quick, negative effects on a URL's presence in Google Search.
Google says while DNS errors are most commonly caused by misconfiguration, network errors may occur before or while Google is crawling the URL. As the errors can occur before the server can respond, there’s no status code to identify issues and diagnosing the error can be challenging.
The help document provides guidance on debugging Network and DNS issues.
All issues mentioned above will generate a corresponding error or warning in the Search Console Crawl Stats report.