Status Code 503: What Does Service Unavailable Mean?

503 Service Unavailable is one of the most common error messages on the Internet and is sometimes unavoidable. Under certain circumstances, however, the status code 503 has a negative effect on the Google ranking of webpages.

You have probably come across the error message “503 Service Unavailable” several times while surfing the web. The 503 status code informs the browser that the desired service or webpage is currently unavailable. There are several possible reasons for this.

Causes for the HTTP Status Code 503

  • Server overload: One of the most common reasons for the HTTP status code 503 is server overload. Particularly in the event of a temporary surge in traffic, the server can no longer respond to all requests and webpages are no longer accessible.
  • Server maintenance: Server maintenance, for example to install new updates, is also often responsible for the status code 503.
  • Spam attacks and faulty programming: Other possible causes for the error message are malware or spam attacks (especially with WordPress pages) or faulty programming.
  • Incorrect configurations: If the server or client is configured incorrectly, this can also lead to a 503. However, this is comparatively rare.

Multiple Formulations

How the status code 503 is displayed differs. The following messages are possible, among others:

  • Statuscode HTTP Error 503
  • HTTP 503
  • HTTP Error 503
  • HTTP Error 503 The service is unavailable
  • 503 Error
  • HTTP Server Error 503
  • Error 503 Service Unavailable

503 and SEO – Risks and Possible Consequences

A status code 503 can have a negative impact in various ways:

  • 503 error messages lead to dissatisfied users. Especially if they occur more frequently and/or for a longer period of time.
  • Google also reacts to this. First, the search engine slows down the crawling of webpages. If the page is not accessible for several days, explains John Mueller from Google, the search engine may even remove it from the index. We therefore advise you to quickly eliminate the cause of the code.

Use “Retry-After” Header

According to Google, it is advisable to use the HTTP header “Retry-After” of the 503 Service Unavailable code during maintenance work. You can use this to inform both users and the Googlebot when the page is expected to be available again.

The combination of the status code 503 and the helpful information in the Retry-After header is also a good replacement for other codes (e.g. 404) in the event of server errors, temporary placeholder pages, downtimes or bandwidth restrictions.

However, even then, the status code 503 is only a temporary solution. In the long term, it can lead to a removal from the index.

Steve Paine