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How to Check HTTP Response Status Codes

October 15, 2021

Whenever you load a page or file on a website, the server hosting that website returns a numerical code that indicates the page’s status. These numbers are called HTTP Response Status Codes and is returned in the HTTP Response Header. You won’t see the HTTP Response Header displayed on the page itself. However, the browser or bot loading the page will see this response code and the code will tell the browser or bot something about the page being loaded.

As an example, if the page loads successfully in response to a request, the website returns a response status code of 200. Or, if the requested page is not found, the status code returned is a 404. If the requested page redirects elsewhere, the status code returned will be a 301 or 302.

How to Check HTTP Response Status Codes

There are a number of tools that can check the HTTP status codes your website’s pages currently return. For a one-by-one analysis of a page, I recommend WebSniffer’s header check tool. When you arrive on the page, you want to enter the URL to the page you want to test. Then click submit for a basic check.

WebSniffer.cc

For a more advanced check, Web Sniffer lets you configure a few extra settings, including changing the user-agent from Web-Sniffer to different browsers or to Googlebot. That provides a helpful way to determine if every browser sees your website the same way and if Googlebot can see the website the same way as a human visitor.

After you’ve submitted, Web Sniffer will give you three pieces of information. First, Web Sniffer will give you the request header. This repeats the settings you had specified on the first step and can generally be ignored. But, if you need to remember what settings you had entered, especially if you used any of the advanced configurations, this request header information can be useful.

Web Sniffer Request Header

The more interesting information, and what we are after, is the HTTP Response Header. In this example, we can see that the requested URL of http://www.matthewedgar.net returns an HTTP response status code of 301, indicating the URL has moved permanently. Within the response header, we can use “Location” to see where this URL redirects to—in this case, it redirects to https://www.matthewedgar.net. That means the non-secure HTTP version of this page redirects to the HTTPS or secure version of this page. This is the expected behavior and, therefore, what we’d want to see here.

Websniffer Response Header

Finally, Web Sniffer also will also show you the content of the returned page if the content-length of the response header is greater than 0. In the case of a redirected page, the content-length is 0—that’s because no content is returned by the server when a redirect occurs. To see an example of this, let’s run a URL that returns a status code of 200.

WebSniffer - HTTP Response 200

Below this table, you will see the content for the status 200 page. This helps you compare what is returned against what you expected to be returned. For example, perhaps you load the page as Googlebot in Web Sniffer and see entirely different HTML code than you see when loading the site in a browser—this would be a big problem for SEO and one you’d want to fix immediately.

How To Check HTTP Status Codes In Bulk

Instead of checking an individual page at a time, you can also check several pages’ response codes at once using tools like HTTPStatus or Knowledge Bull’s. Alternatively, you can use a tool like Screaming Frog to check this as well. After running a crawl, you will see a list of all pages contained on your website and their respective status codes. Pay attention to any pages that don’t return a status 200.

Reviewing status response codes in Screaming Frog
Reviewing status response codes in Screaming Frog

Checking HTTP Status Code via JavaScript and PHP

Along with the tools discussed above, you can also obtain the HTTP status via code. Using JavaScript, you can get the HTTP status code of a URL via an XMLHttpRequest. You can see an implementation of that on this JSFiddle. One note: this code only works if you are checking on the same domain. For example, to check a page on Elementive’s site, I’d have to run this code on Elementive’s domain and pass in relative URLs, such as:

getStatus( '/web-analytics');

However, this code will not work on external domains or subdomains for security reasons. If you try to run this JavaScript code to check status codes on an external domain, you will get an “Access-Control-Allow-Origin” error message.

As an alternative, you can also check the page’s status code via PHP. This will work for the same domain and for (most) external domains. For example, this code will return the response code for the stated URL (“HTTP/1.1 200 OK” in this example).

$url = 'https://www.elementive.com/web-analytics/';
$headers = get_headers($url, 1);
echo($headers[0]);

What Status Codes Are Returned by a Website?

You can see all the HTTP status codes on Mozilla’s list, but there are only a few commonly seen HTTP status codes that you really need to understand. These are the HTTP status codes that have the greatest impact on UX and SEO:

  • 200 – Ok – the page is successfully loaded – normal
  • 201 – Created (see below)
  • 301 – Permanent redirect
  • 302 – Temporary redirect (technically “Found”)
  • 304 – Not Modified (see below)
  • 307 – Temporary Redirect
  • 308 – Permanent Redirect
  • 403 – Forbidden (i.e. password protected)
  • 404 – Not Found
  • 410 – Gone/removed page
  • 500 – Internal server error
  • 503 – Service unavailable

You want to make check the HTTP status code every page on your website returns to make sure the code accurately reflects the nature of the page. If the nature of the page and the status code are in conflict, search robots can be confused by your website and that confusion will affect rankings and, ultimately, traffic.

The most common example of this status vs. page conflict is a Soft 404. With a soft 404, the HTTP status code returned is 200, which would indicate everything is normal. However, with a Soft 404, the page content says the requested file could not be found. In this case, the HTTP status code should be a 404 to indicate the webpage is not found and to match the page’s content.

To begin identifying issues, like Soft 404s, that might exist on your website, the first step is to check the HTTP response code each page returns on your website.

Reviewing Specific Response Codes

Status 200 vs. Status 201

One of the response codes returned might be a status 201 instead of the expected status 200. A status 201 indicates that a resource has been created and the expected behavior is that the page returning the 201 should provide a location indicating where to locate that newly created resource. More often than not, you’ll see this status code used within APIs instead of websites. However, certain web apps do use 201 response codes in response to user behavior, such as after a user uploads a new file or adds a post to a forum. If your website is returning a status 201 you want to make sure it is used appropriately and that the location to the new resource is correctly stated as part of the response. For example, if you run a status 201 page through WebSniffer, you should see a line for Location in the HTTP Response Header table.

Checking 301s & 302s: Following Redirect Chains

If any URLs return a 301 or 302 response code, that means the URL redirects somewhere else. In these cases, it is helpful to know where those URLs redirect. As well, you’ll want to check if the redirect happens in one step or multiple steps. There are several tools for this but one we recommend is a simple and free tool called WhereGoes.com. To begin, enter in a URL that redirects, in this case, I’ve entered in “elementive.com/chain”. Then click “Trace URL”.

WhereGoes.com - A Tool for checking redirect destinations

The results will then tell you where this URL redirects to. In this example, /chain redirects to chain-1, which redirects to chain-2, which redirects to chain-3, which redirects to chain-4, and chain-4 redirects to Elementive’s home page.

WhereGoes.com Redirect Chain Trace

For more help on redirects, including how to address redirect chains and whether you should use 307 or 308 status codes, check out my in-depth guide to redirects.

304: Not Modified Response Code

When checking your website’s HTTP response codes, you might also see a 304 response code returned. Although it is sometimes considered an error, it isn’t necessarily a problem. A 304 response code indicates the file requested has not been modified since the previous request. Instead of loading the file, the browser or bot requesting this file can use a cached version instead. In some cases, this can help with a website’s speed. However, using a 304 still makes a request to the server because the server has to check if the requested file has been modified since a particular date. If you have 304 response codes returned for files on your website, you want to determine if those are helping with the website’s speed or if other forms of caching may work better.

404 vs. 410 Status Codes

When the webpage is not found, the HTTP response status code should either be a 404 or 410. As mentioned above, you also want to watch out for Soft 404s too. For more about 404 vs. 410, Soft 404s, and other similar errors to check for on your website, see my guide to website error pages.

Need Help?

If you have questions about what response status codes your website returns, or want help resolving any related problems with those response codes, please check out my book, Tech SEO Guide, or contact me.

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