How to Check HTTP Response Status Codes
By Matthew Edgar · Last Updated: March 17, 2023
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, called an HTTP Response Status Code as part of the HTTP Header. The status code says if the page is operating correctly, is in error, requires authentication, and more. The HTTP Response Status Code is returned in the HTTP Response Header, which contains other details about the page. You won’t see the HTTP Response Header or the status code displayed on the page itself. Instead, the browser or bot loading the page will see this response status code and will use that information to help load and process the page.
There are a number of different response status codes that can be returned. As an example, if the page loads successfully in response to a visitor’s request for that page, the website will return a response status code of 200. With that status code, browsers and bots know to load the page as usual. Alternatively, if the requested page is not found, the status code returned will be a 404. Browsers and bots know to handle this type of HTTP status code as an error page. If the requested page redirects elsewhere, the HTTP status code returned will be a 301 or 302. With a 301 or 302 status code, browsers and bots will process the redirect to a different URL.
How to Check HTTP Response Status Codes
There are a number of tools you can use to check the HTTP status codes your website’s pages currently return. For a basic one-by-one analysis of a page, you can use header check tool like REDbot. Enter the URL of the page you want to test then click the arrow button to fetch the page headers.
For a more advanced check, you can use WebSniffer to configure the request type, HTTP version, and the user-agent. It can be helpful to change the user agent to Googlebot to see what HTTP status codes are returned when Google is crawling the website.
In the returned response, we can locate the HTTP response status code in the HTTP Response Header. In this example, we can see that the requested URL 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 (secure) version of this page. This is the expected behavior and, therefore, what we’d want to see here.
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.
Alternatively, you can use a tool like Screaming Frog or Jet Octopus to check the response status 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.
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. To check the status code of the page https://example.com/page-url, I’d use the code:
Checking HTTP Status Code in PHP
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 status code for the stated URL (“HTTP/1.1 200 OK” in this example).
$url = 'https://www.elementive.com/';
$headers = get_headers($url, 1);
What HTTP 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 more details below)
- 301 – Permanent redirect
- 302 – Temporary redirect (technically “Found”)
- 304 – Not Modified (see more details below)
- 307 – Temporary Redirect (learn more about 307 redirects)
- 308 – Permanent Redirect (learn more about 308 redirects)
- 401 – Unauthorized (invalid credentials, see more details below)
- 403 – Forbidden (permission denied, see more details below)
- 404 – Not Found
- 410 – Gone/removed page
- 429 – Too many requests (see more details below)
- 451 – Unavailable For Legal Reasons
- 500 – Internal server error (see details below)
- 503 – Service unavailable (see details below)
When you check your website’s response codes, you want to confirm the HTTP status code returned by every page on your website 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 code versus 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.
Need help on redirects? For more information about redirects, including how to address redirect chains, check out my in-depth guide to redirects.
There are several tools to check redirects and identify redirect chains, including WhereGoes.com and HTTPStatus. Using HTTPStatus as an example, begin by entering a URL (or multiple URLs) that redirects. For example, I’ve entered “https://www.elementive.com/redirect/chain”, which redirects to the website’s home page through multiple redirect hops.
The results will then tell you where this URL redirects to. In this example, /redirect/chain redirects to chain1, which redirects to chain2, which redirects to chain3, which redirects to chain4, and chain-4 redirects to Elementive’s home page.
We can see similar results in WhereGoes.
304: Not Modified Response Code
A 304 HTTP response code means the requested file has not been modified since the previous request was made. Instead of loading the file, the browser or robot requesting this file can use a cached version of that file instead. To accomplish this, the browser (or robot) sends the last modified date for the cached file via the If-Modified-Since HTTP Header. The server then checks if the file has been modified since the stated date—if the file has been modified, then the file is sent from the server to the browser but if the file has not been modified since that date, then no file is sent.
Although the 304 response code is sometimes considered an error, it isn’t necessarily a problem. In some cases, the 304 response code can help with a website’s speed because fewer total files need to be downloaded from the server and can be loaded from the cache.
401 vs. 403 Status Codes
Both the 401 and 403 status codes can both be used to indicate restricted access to a file or directory. By restricting access, you are telling robots from search engines not to index the page. The difference is that a 401 is about authentication while a 403 is about permission.
A 401 status code indicates authentication failed and is often used with a login page. For example, let’s say you have a password-protected area of your website. When a visitor (or bot) provides invalid login credentials, a 401 response status code says that proper credentials were not provided. (A 401 must also include WWW-Authenticate in the header with authentication methods.)
A 403 status code indicates the requested file or directory is forbidden because the person or robot making the request does not have permission to access the file. This is often used to block off large sections of the website that people and robots should not be able to view. For example, you would not want robots or people to see your entire image library, so the main page of the image library could return a 403 status code. This is what WordPress does by default, as you can see on my website:
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.
429: Too Many Requests
A 429 response status code can be returned to tell a browser or robot that it is requesting too many files from the website and is overextending the server limits. This status code is used alongside rate limiting. Typically, this response code is not needed but can be useful on larger websites dealing with a high volume of requests.
Google recommends using this status code as part of emergency measures to limit crawls from Googlebot when Google’s crawls are harming website availability. The first step is to establish a method of detecting and responding dynamically if Googlebot is making too many requests. If Googlebot does make too many requests, approaching or exceeding the limit, the server should return a 429 response status code. If this status code is returned for more than a few days, it can permanently alter how frequently Google crawls the website.
Configuring this type of limiting for Googlebot can be complex. Given that, the easier answer Google recommends is to use robots.txt directives to limit crawls.
5xx: Server Errors
The status code for any server error should be within the 5xx class. It is important to not return a status 200 with a server error because that tells robots the page is operating correctly. Similarly, returning a 404 with a server error confuses robots about what the error is. There are different types of 5xx response codes that can be returned:
- A 500 response code is the most generic response code to use in the event of a server error. While generic, it still communicates that an error has occurred. Where possible, you want to use a more specific status code.
- A 501 indicates that the server failed because the functionality requested is not available yet. This isn’t very commonly used and is not explicitly supported by Googlebot.
- A 502 indicates the server received an invalid response. For example, Cloudflare received a request for a file but couldn’t fetch that file from the website’s server.
- A 503 indicates the website is down for maintenance or is currently overloaded. This is the most common status code to use for server errors. You can also return a Retry-After header to indicate when the service will be returned (a Retry-After header is easier to return for planned maintenance when there is an established time window).
Monitoring Status Code Usage
It is also important to monitor what status codes Googlebot is encountering when crawling your website. One way to do this is in Google Search Console. In the sidebar, click on Settings, then under Crawling click on “Open Report”. On the main page, you can view crawling By Response. Clicking on any of the status codes will provide a list of pages that were returning that response code and the date of the last crawl.
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.