HTTP server responses are responses that the server delivers when accessed by a client. The server can use status codes to tell the browser whether the request to get the code was successful or not. Status codes are divided into different classes. The most important status codes are 200, 300, and 404.
Server Responses classification by classes
- 1xx codes: These codes inform the client that the request has been processed.
- 2xx codes: These status codes indicate successful data retrieval.
- 3xx codes: This code indicates a redirect from one URL to another. These redirects can be temporary or permanent.
- 4xx codes: This vode indicates client errors. For example, it might be a false request for a URL that is not available on the server.
- 5xx codes: This class includes server side errors such as unavailability or internal errors.
- 9xx codes: These proprietary errors are not caused by the server or client, but by the network. Reloading the page can resolve these error messages.
- All status codes are precisely classified and defined according to RFC-7231.
Important HTTP server responses and their meaning for search engine optimization
The server sends many different status messages depending on the status classes. The following status codes are particularly important for search engine optimization:
Server Response 200: OK
This code is returned by the server if it can correctly return the request from the browser. To display the code and page content, the server must first accept the request. Then the desired source should be available on the server and the server should output it correctly. Thus, the output of the “200 OK” code is a prerequisite for the website to function properly.
Server Response 301: „moved permanently“
The code known as a 301-forwarding or redirect is especially important in the context of duplicate content. With the "htaccess" file, URLs could be permanently redirected to another URL to avoid duplication in the Google index. In this case, the "old" URL is no longer called by the browser, but the "new" URL is displayed immediately. The 301-forwarding transfers link juice even if the old resource is no longer valid.
Server Response 302: Temporary forwarding
This temporary redirect works similarly to a 301 redirect. However, the old URL remains valid. Same as with the 301 code, the 302 redirect also inherits PageRank.
Server Response 404: 404 error „not found“
If a 404 code is displayed, the requested resource is no longer available or not available at all on the server. This code is issued, for example, if the user entered an outdated URL for which there is no redirection to the new URL. The status code "404 not found" is also displayed if an invalid URL is entered into the browser.
In the context of search engine optimization, it is recommended that the server actually outputs its own error page when it is “not found”. According to Google, accumulating 404 error pages does not negatively impact rankings. However, many 404 errors can impact the usability of a website. For this reason, it is recommended that you create error pages in such a way that the user is offered an alternative and stays on the page.
404 errors can be easily checked using the Google Search Console. If the server does not display a 404 error page even though the resource does not exist, this is also called Soft 404 errors. This should be avoided by whatever means. Since Google can rate them as a sign of poor site maintenance or even spam, the result of the client's request does not match the actual server response status.
Server Response 500: „service unavailable“
If such server error appears, it means that it is an internal server error. In this case, the web host must be operating. Or the htaccess file on the webserver needs to be adapted.
Server Response 503: Maintenance
If the server issues this code, maintenance may prevent access to the server.
Checking the server responses
If you want to cancel the status code of a website, you usually need a suitable tool. There are corresponding plugins for browsers such as Firefox or Google Chrome that you can use to display the URL codes. Many web analysis tools also allow you to check the status of the URL.
Analyzing the server responses in the Site Experience
The Indexability/Server Responses tab in the Site Experience provides you a summary overview of the server responses for the individual URLs of the crawled domain. The numbers of risks and potentials that arise from the server responses are also shown. At the bottom of the page there is a detailed list of all crawled URLs, including their server responses and forwarding chains, so you know exactly where optimization potential exists and what can be done as quickly as possible.
The Search Experience section Link Analysis/Broken & Redirected Links also gives an overview of all 300, 400 and 500 server responses, as in case of doubt they can negatively impact visibility and traffic and require quick action.