HTTP status codes and what they mean for SEO

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HTTP status codes, like 404, 301, and 500, might not mean much to a regular visitor, but they are incredibly important for SEO. Not only that, search engine spiders, like Googlebot, use these to determine thehealth of a site. These status codes offer a way of seeing what happens between the browser and the server. Several of these codes indicate an error, for instance, that the requested content can’t be found, while others simply suggest a successful delivery of the requested material. In this article, we’re taking a closer look at the most important HTTP header codes and what they mean for SEO.
What are HTTP status codes, and why do you see them?

An HTTP status code is a three-digit message the server sends when a request made by a browser can or cannot be fulfilled. According to the official W3C specs, there are dozens of status codes, many of which you're unlikely to come across. If you need a handy overview of status codes, including their code references, you can find one on HTTPstatuses.com.
To fully understand these codes, you must know how a browser gets a web page. Every website visit starts by typing in the URL of a site or entering a search term in a search engine. The browser requests the site’s IP address for the associated web page. The server responds with a status code embedded in the HTTP header, telling the browser the result of the request. When everything is fine, an HTTP 200 header code is sent back to the browser in conjunction with the website's content.
However, it is also possible that there’s something wrong with the requested content or server. It could be that the page is not found, which gives back a 404 error page, or there might be a temporary, technical issue with the server, resulting in a 500 Internal Server Error. These HTTP status codes are an important tool for evaluating the health of the site and its server. If a site regularly sends improper HTTP header codes to a search engine indexing its contents, it might cause problems that will hurt its rankings.
Here's part of the HTTP header for a web page, with a 200 OK message:
HTTP/1.1 200 OK
Date: Fri, 03 Mar 2023 06:44:24 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Cache-Control: public, max-age=604800, s-maxage=604800, stale-while-revalidate=120, stale-if-error=14400
Different ranges

There are five ranges of HTTP status codes, defining different aspects of the transaction process between the client and the server. Below you’ll find the five ranges and their main goal:

1xx – Informational
2xx – Success
3xx – Redirection
4xx – Client error
5xx – Server error

If you ever try to brew coffee in a teapot, your teapot will probably send you the status message 418: I'm a teapot.
Most important HTTP status codes for SEO

As we've said, the list of codes is long, but a few are especially important for SEOs and anyone working on their own site. We’ll do a quick rundown of these below:
200: OK / Success

This is how it probably should be; a client asks the server for content and the server replies with a 200 success message and the content the client needs. The server and the client are happy — and the visitor, of course. All messages in 2xx mean some sort of success.
301: Moved Permanently

A 301 HTTP header is used when the requested URL is permanently moved to a new location. As you are working on your site, you will often use this, because you regularly need to make a 301 redirect to direct an old URL to a new one. If you don’t, users will see a 404 error page if they try to open the old URL and that’s not something you want. Using a 301 will make sure that the link value of the old URL transfers to the new URL.