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What are HTTP status codes?

An HTTP status code is a response sent back by the server to indicate the status of a website request. It serves as a status update regarding the URL you are visiting and is important for visitors to your website.

An HTTP status code indicates whether your visit to the URL was successful. Status codes are three-digit codes, where the first digit indicates the category of the URL status.

An HTTP status code isn’t always visible, but it’s indispensable for crawlers, developers, and marketers. The most well-known HTTP status code is the 404 code: on a website, this indicates to the user that the URL no longer exists. With tools such as the Chrome extension SEO Pro Extension, it’s possible to view HTTP status codes.

The Different Groups of Status Codes

HTTP status codes are divided into five different groups. The groups are numbered from 1 to 5. The different groups are:

1xx (Informational): These status codes indicate that your request is still being processed. They are a temporary response from the server.
2xx (Success): These status codes indicate that everything is okay.
3xx (Redirect): These status codes indicate that a URL has been moved.
4xx (Client error): These status codes indicate that the page no longer exists.
5xx (Server error): These status codes indicate that something is wrong on the server.

Why are HTTP status codes important?

For a website visitor, a status code usually doesn’t matter, but for crawlers, they are crucial. I’ll explain the implications for website visitors and crawlers below.

Users often don’t notice an HTTP status code, since most pages have a 2xx code. After all, in the case of a 301 redirect, the user ends up at a different URL. Moreover, a website visitor often doesn’t even realize that the URL has changed.

For 4xx and 5xx status codes—such as a 404 error—it’s a different story. When a 404 error occurs, a browser displays the 404 page to users, and when a 500 status code occurs, it displays a standard error page. This way, the user has visual confirmation that, for example, a page no longer exists or that there is a temporary error on the server.

HTTP status codes are essential information for crawlers. There are a number of reasons why they are important:

This way, crawlers know which pages should be indexed and which ones shouldn’t.
It is clear to crawlers which pages have been permanently moved to a different URL.
Crawlers know which pages are experiencing issues with the website or the server.
Crawlers know whether they have successfully loaded a page.

HTTP status codes provide crawlers with efficient information about the accessibility, status, and location of pages. This helps make crawling the internet more efficient, so they are an important part of SEO.

The Most Common Status Codes

There are a total of 60 status codes, and you’ve probably never heard of most of them. The four most important status codes are explained below. All status codes are explained with clear descriptions and funny images on HTTP Status Dogs.

200 OK

The 200 status code indicates that everything is fine. This means the page can be loaded without any problems.

301 Permanent Redirect

The 301 status code (also known as a 301 redirect ) is a status code that indicates that the visited URL has been permanently moved to a different URL. The HTTP header containing this status code also includes the URL to which visitors and crawlers should be redirected.

There are two types of redirects: 301 and 302 redirects. The difference between a 301 and a 302 redirect is that a 301 redirect indicates that the URL has been permanently changed. That is why link equity is also passed on. This is not the case with a 302 redirect.

404 Not Found

The 404 status code indicates that a page no longer exists. This displays the well-known 404 page on a website. You want to avoid as much as possible having a visitor land on a page with a 404 status code, because this detracts from the user experience.

500 Internal Server Error

The 500 status code appears when there is a problem with your server. In that case, the website becomes completely inaccessible, and the server returns the 500 status code. This may be due to incorrect PHP files, a temporary outage, or an incorrect database connection. It’s important to resolve this as quickly as possible, because in most cases, your entire website will be inaccessible.

Look up HTTP status codes in Google Search Console

Google keeps track of the status codes the crawler encountered during its visits to your website. Under “Pages” in the “Indexing” section, you’ll see an overview of all indexed and non-indexed pages.

Under the heading “Why Pages Aren’t Indexed,” you’ll see a list of the various reasons. Here, for example, you can see which 404 errors and 301 redirects Google has encountered.

You can also view all status codes using Google’s crawl statistics in Google Search Console. You can then use this information to resolve issues such as 404 errors or 500 errors.

Sources

[1] https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

This article was written by Jarik Oosting

With a passion for SEO and an unmatched drive to achieve results, Jarik Oosting is the driving force behind SmartRanking. With more than 15 years of experience in the field, Jarik has built up a wealth of knowledge, ranging from technical SEO to complex migrations. As the founder of SmartRanking, he has assembled a team of like-minded SEO specialists who help companies achieve their online growth goals. He is also the author of the book *GEO – Being Visible in AI Answers*, which explores how companies can remain discoverable as AI search engines reshape the search landscape, and he is a frequent speaker.

His academic background in Information Science at the University of Groningen, with a specialization in Natural Language Processing, gives him a unique perspective on the world of SEO. For Jarik, it’s not just about search engine visibility, but about sharing knowledge and guiding companies toward sustainable online success.

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