What are HTTP codes?
Website servers on the internet help to identify the cause of a problem when a web page or other resource does not load properly by giving standard response codes called HTTP status codes.
Why are HTTP codes important?
If you own a website, HTTP codes are essential for understanding why your site is not loading. They can help to point out what the issue may be and how it should be fixed.
How do HTTP codes impact SEO?
Google shared a document that covers some of the most common HTTP status codes and network errors encountered by Googlebot.
Googlebot crawls the content from pages that serve a 2xx status code, but it does not guarantee to index. Google will show Search Console for soft 404s in 204 statuses.
The difference between 301, 302, 303 & 307 is that the first one sends a stronger signal than any of those other status codes. 304 signals to Google which URL should be considered canonical and it doesn’t have an effect on indexing but recalculate its signals for the page instead.
A 4xx status code means the content doesn’t exist, and Google’s search index will be updated to remove it. A 429 error is different because Googlebot couldn’t access a URL due to the server being overloaded. Those URLs are preserved in search results so users can find them later on after traffic has decreased.
Googlebot may temporarily slow down crawls of previously indexed URLs that now have a server error if they continue to serve 5xx status codes.