HTTP Status Codes SEO Specialists Should Know


When operating websites, you may come across terms like “HTTP status code,” “404 error,” and “301 redirect.” These terms deal with how search engines handle URLs, so if you’re in charge of SEO or specialize in it, you should have an understanding of what they mean. This article explores terms and important details that all SEO experts should be familiar with.

What are HTTP status codes?

Figure 1 below shows the relationship between the browser and your smartphone or computer and the web servers when viewing web pages.

(Figure 1: The relationship between clients and web servers)

HTTP status codes are 3 digit numbers that express the result of the web server processing contained in the HTTP response.

(Figure 2: The HTML files and execution results are returned in the HTTP response)

The 3-digit numbers have several meanings including the process succeeding, a redirect (transfer) occurring, or an error. As an SEO specialist, you don’t need to know the detailed workings of internet communication, but you should know how HTTP status codes work because they deal with how search engines handle web pages. 

Why SEO specialists need to understand HTTP status codes

The major premise of URLs indexed by search engines is that they’re viewable by users (because if they aren’t, the URL displayed by the search result returns errors, lowering the convenience of search engines). In other words, it’s best for SEO specialists to understand HTTP status codes to check whether the URL they wish to index can be viewed without any issues.

Furthermore, as an SEO specialist, you may be tasked with moving or deleting web pages and content, as well as changing URLs. It’s important to understand status codes because you’ll have to ensure that each URL returns an appropriate status code when changing URLs. Otherwise, you run the risk of decreasing organic traffic.

The types of HTTP status codes

HTTP status codes can be divided into 5 categories: 1xx, 2xx, 3xx, 4xx, and 5xx. We’ve compiled the major codes into a chart. The codes in bold type are the ones you should especially know if you’re working with SEO.

Reference: HTTP response status codes

① 1xx (informational)

1xx codes show that the information is being processed. You won’t see these codes in search console tools like Google Search Console, but it won’t hurt to have a basic understanding of them regardless.

② 2xx (success)

The 2xx codes show that the communication was successful. URLs you wish to index should return “200 OK” or “201 Created.”

③ 3xx (redirection)

The 3xx HTTP status code shows that a redirect has occurred.

④ 4xx (client error)

4xx codes suggest that there are errors on the client-side. It shows that there is a problem with the client (user) request. URLs returning these status codes won’t be indexed.

⑤ 5xx (server error)

5xx status codes suggest that there are issues on the server-side. It means that the server failed to process the request. Crawling on URLs that return this category of status codes will decrease in frequency. URLs indexed will stay that way for a period of time before being deleted from the index.

*Source: How HTTP status codes, and network and DNS errors affect Google Search 

Terms relevant to HTTP status codes SEO specialists should know

This chapter will briefly cover terms you should know as an SEO specialist.

① 301 and 302 redirects

Redirects refer to transferring users who access an existing URL, to a separate URL. The types of redirects are shown below. 301 redirects and 302 redirects refer to redirects that take place on the server-side.

— Redirects implemented on the server-side

We recommend using tis method, implemented on the server-side, when changing URLs you want to index. The difference is that 301 redirects are permanent, while 302 redirects are temporary.

— Redirects via the meta refresh tag

Alternatively, you can use the meta tag if redirecting on the server-side is difficult. Place it in the head section of the HTML or with the HTTP header in server-side code.

— Redirects using JavaScript

Another alternative is using JavaScript to redirect. Keep in mind that after crawling, Google bot may fail to render due to various reasons, which may cause it to miss several detection of redirects.

*Creating a screen displayed to the users based on HTML files, and also includes JavaScript executions.
*Source: Redirects and Google Search

② Soft 404

Soft 404 refers to URLs returning 200 status codes even when there is no content (or if the content has been deleted). The search engine will crawl the URL as a candidate for indexing because of this, but once it detects that there is nothing to show users arriving from search results, it will deem the page to be a soft 404 and not register it on the index.

(Figure 3: A page determined to be a soft 404 by Google)
*Source: How HTTP status codes, and network and DNS errors affect Google Search

③ Custom 404

Custom 404 refers to a customized web page for users to tell them that there is no content (or the content has been deleted). When operating websites, you’ll inevitably come across 404 pages, but those without customization will simply display an error message.

(Figure 4: A 404 page displaying nothing but the error message)

Customizing the page to communicate to users that there is no content while displaying other messages may prevent users from leaving. The 404 will not be displayed in search results, but it’s important because it contributes to user convenience.

(Figure 5: An example of a customized 404 page)

Google has provided the following hints with regards to custom 404s. 

  • Tell visitors clearly that the page they’re looking for can’t be found. Use language that is friendly and inviting.
  • Make sure your 404 page has the same look and feel (including navigation) as the rest of your site.
  • Consider adding links to your most popular articles or posts, as well as a link to your site’s home page.
  • Think about providing a way for users to report a broken link.

*Source: Fixing Soft 404 Errors

How to check HTTP status codes

You can check using the developer tools on Google Chrome.

  1. Open Google Chrome and press the [F12] key to open developer tools.
  2. Access the page you wish to check
  3. Click on the “Network” tab to check the status.

(Figure 6: Checking the HTTP status code using developer tools)


This article explored HTTP status codes and relevant terminology. Server errors are usually handled by engineers, but SEO specialists should have a firm grasp of the terms covered in this article to make the workflow smoother. When changing websites resulting in altered URLs, it’s crucial to properly configure redirects to prevent adverse effects on your website traffic. If you’re looking to transfer your page URL, we can provide assistance while keeping in mind the effects on search engines.

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