5XX status codes are returned when a server has an error responding to an acceptable client-request made in the browser.
Often-times these can be avoided by refreshing a webpage, but not always.
Server errors should be worked on as soon as they are found in order to ensure that all users have a seamless experience.
The most common 5xx server errors are 500, which is a general “Internal Server Error”, as well as the 503, “Service Unavailable” error.
Other server error types include:
501 – “Not Implemented”
502 – “Bad Gateway”
504 – “Gateway Timeout”
506 – “Variant Also Negotiates”
507 “Insufficient Storage”
508 – “Loop Detected”
509 – “Bandwidth Limit Exceeded”
510 – “Not Extended”
How 5XX Status Codes Impact SEO & User Experience
5XX status codes are seen as a poor signal by search engine ranking bots, as if a bot encounters too many of them may penalize your site for poor UX (as the user would also experience the same errors).
Users would also be very frustrated, and perhaps become distrusting of a site that has too many 5XX errors, as it can be seen as poor maintenance/upkeep of your web property.
5XX errors encountered during crawls also waste crawl budget, so you always want to be sure that your servers & hosting are running as well as possible.