HTTP status codes are like brief notes from servers that are put on top of web pages, but aren’t in fact a part of them. What they are, are messages from servers that notify you how different requests are received by servers.
Basically, whenever browsers interact with servers, such messages are returned. However, users may not see them at all in many cases. But if you own or optimize websites, it’s critically important for you to understand HTTP status codes. They’re crucial when it comes to diagnosing and patching up various configuration errors on your website.
In this blog post, we’ll look at the most common HTTP status codes and errors, as well as explain how to handle them to avoid making a mess of your website.
Side-note: If you want to check the status codes of your site’s web pages, plus get a detailed SEO audit, you’re welcome to make use of our Website Audit tool.
What status code classes are there?
Each request has HTTP server response data that includes a three-digit number that specifies the request’s result. These response codes are broken down into 5 distinct classes. Let’s quickly go through each one of them:
- 100’s status codes are informational codes that let clients know that so far everything is going according to plan. The server has received the request and is processing it, but no response is available yet. Such status codes aren’t usually displayed on the screen, but serve as internal codes that only browsers refer to.
- 200’s status codes are success codes that indicate that the request was received, understood, accepted and processed successfully by the client. Again, these status codes are used internally by browsers to confirm the request’s success and current status.
- 300’s status codes are redirection codes that simply show that the requested content has been temporarily moved to another URL.
- 400’s status codes are client errors that signal that something’s wrong with the request. They are often related to security issues, but can also be returned if the client times out or if the request was entered incorrectly.
- 500’s status codes are server errors that specify that the server found the requested web page, but can’t grant access to it. Ultimately, the request can’t be processed.
I want to draw your attention to the fact that not every status and error code can be seen, in fact, most of them aren’t shown to users at all. However, you can check them by inspecting a page via your browser (Ctrl+Shift+C to open the Chrome Developer Tools in Inspect Element mode). Just go to the Network tab and refresh the page to get a list of the statuses of each element on the page, including the page itself:
Now, let’s take a close look at the most common server responses and how they need to be handled.
Common HTTP Status Codes
Before we continue, I want to point out that there are more than 40 different server status codes, but it’s likely that you won’t run into more than a handful of them in your work. So, if you’re in charge of a website and its SEO processes, it’s imperative that you understand them so that you know what to do when you’re faced with HTTP status code issues.
Without further ado, here’s a list of the most common HTTP status codes:
301 Moved Permanently
The HTTP 301 Moved Permanently status code indicates that the URL requested by the client has been moved to a new location. Browsers follow 301 redirects without asking users to perform an action.
The 301 status code is typically used when switching a website from HTTP over to HTTPS, but it is also employed when setting up access to the website mirror, during URL trailing slash configuration, as well as when transferring a part of the site or the entire website to a new domain.
This redirect is highly recommended if your goal is to transfer the SEO ranking and authority of an old web page to a new one. But simply changing the URL without updating content will have a negative impact on the indexation of new changes. Think about it: You send a new signal to search engines that you want the new page to come up in search, but since the old URL has a lot of authority, Google doesn’t want to replace it with the new page.
Pro Tip: Don’t ever redirect users from a deleted URL to your homepage. Such redirects are treated as soft 404s by Google, meaning that the search giant won’t pay any attention to them, won’t pass the PageRank or any other signals from the old URL to the new one. Instead, lead users to a page that’s similar to the destination page.
Additionally, avoid redirect loops as they prevent users from getting to the target page. In other words, steer clear of using link chains that include a link that’s redirected to a URL that’s already part of the same chain.
Plus, Google doesn’t index beyond the 4th or even 3rd redirect in a redirect chain. For this reason, it’s important not to use multiple redirects as each new one will result in a ranking weight loss. Multiple redirects will confuse Google as to where all of the page authority should be directed. So, just cut out the middleman and redirect the first page directly to the last one you have set up. On top of that, you can even remove 301 redirects as time passes to reduce the server load.
The 302 Found status code is very similar to the 301 code, but the 302 status code was created for situations when a website isn’t moved permanently, but only temporarily.
Basically, browsers follow the 302 code automatically, and it indicates that the page was successfully found, but it has been temporarily moved to a new location. As a general rule, it should only be used for short content maintenance processes, when you ultimately intend to take your website visitors back to the old web page.
When you set up the 302 redirect, you tell search engines that you plan on using the old URL again in the future. As a result, the temporary new page doesn’t get any traffic value or page authority from the original URL.
Pro Tip: If you leave the 302 redirect in place for too long, Google will end up treating it as if it’s a 301 redirect. Furthermore, make sure to check that your website doesn’t have any 302 redirects that are supposed to be 301 as this is a very common mistake.
304 Not Modified
The browser sees the 304 Not Modified HTTP status code when a web page is up to date with the cached copy on the server. Essentially, this means that the page hasn’t changed since the last visit.
To elaborate, when browsers store data in their cache, they store the Last-Modified header data as well. In turn, this enables browsers to know exactly when the page was last modified. And when search engines look at the page and see that both header values are the same, the server returns the 304 code.
This code can actually be used to speed up website indexation. For example, as crawlers are going through your website, they’ll stumble upon multiple pages. And if they learn that one or several pages have not been changed in any way, they’ll skip them, ultimately, enabling more pages to get indexed.
Pro Tip: Every SEO expert is expecting to see the 200 OK status code as an indication that the request is successful, but the 304 status code basically means the same thing. As a rule of thumb, new pages and first page visits should get the 200 code, and every subsequent visit should produce the 304 code.
The 403 Forbidden status code indicates that the user doesn’t have permission to access the requested web page. This one is pretty straightforward.
There are several reasons why this status code can appear. For example, the user is logged into the website, but doesn’t have the necessary permission to access its closed-off internal network.
Other cases when the 403 status code can appear include situations when the index file for the main page is incorrect. The index file should be called “index” and have the *.shtml, *.html, *.htm, *.phtml or *.php extensions, so make sure to check that that’s the situation in your case.
Moreover, when you switch over to HTTPS, the 403 status code may appear if the Domain Name System (DNS) cache hasn’t been updated yet. Best practices suggest you wait until the cache gets updated, but if it’s a matter of life and death, clear your DNS cache immediately.
Pro Tip: Pages that produce the 403 response code will ultimately be removed from the index, which is why Google advises to use the 404 status code for this instead.
404 Not Found
Probably one of the most well-known status codes in SEO is the 404 Not Found error. This code indicates that the server hasn’t found anything matching the requested URL, but a network connection between the server and the client has successfully been established.
Now, don’t worry if you see a lot of 404 pages in your Google Search Console account. Google is simply letting you know which pages are deleted and it’s up to you to check if everything’s okay. But make sure to remove every link to the deleted pages from your site, so that you don’t confuse visitors as they navigate it.
We usually see this error code when we manually enter a wrong URL into the browser and, as a result, try to access a page that doesn’t exist. However, it can also appear if the server admin deleted a file without first redirecting the URL to a new location that’s valid. To solve the problem, you need to check the requested URL, fix it yourself or wait for the admin to do it.
Pro Tip: Pages that display the 404 status code aren’t indexed and don’t pass any authority, which is why some SEO experts employ a soft 404 page instead that returns a page notifying users that the page doesn’t exist along with the 200 status code. But this is considered bad practice because the success code tells Google that there’s a real page at that URL. Ultimately, the page may end up getting listed in SERPs, and the search giant will continue its attempts to crawl non-existent URLs instead of crawling your actual pages.
Setting up the 404 page for your site
The 404 page used to look like a solid wall of code, but now that times have changed, it has become a lot more creative. However, you must keep in mind that users came to your web page with a specific request, and your job isn’t just to entertain them with cool images, but to help them find what they’re looking for. So, make sure to add your website navigation or a contact form to your 404 pages, especially if they are still seeing traffic.
Now, if your content management system didn’t generate a 404 page for your website, you can create one yourself. Here’s how you can do it:
404 page via htaccess
The simplest way to set up a 404 error page on your website is by directly entering the error message, such as ErrorDocument 404 “<H1>Not Found</H1>”, into the .htaccess file itself. You should get something like this:
404 page via PHP
As for creating a 404 page via PHP, in a nutshell, you can use the header function.
404 page via WordPress
You have several options when it comes to creating a custom 404 page in WordPress:
- Edit the existing 404 page offered by your theme.
- Add a custom 404 page if your theme doesn’t offer one.
- Use a 404 plugin.
You can get all of the details on how to do it here.
The 410 Gone status code indicates that the requested website is no longer available on the server and no forwarding address is known. And because Google’s URL Inspection Tool labels 410 codes as 404 as well, you’ll end up seeing even more 404 page errors in your Google Search Console.
This status code is typically used on pages that have low trust, don’t have any links as well as on permanently deleted ones. For example, let’s say you no longer offer a particular service on your website and want to stop driving traffic that’s searching for the non-existing page. This is where the 410 status code comes into play.
Since Google doesn’t technically treat 404 and 410 errors the same way, you can use a temporary custom 410 page to provide search engine robots with a more accurate status and information that the old link should be removed from the crawl index. Consequently, this can stop the inflow of unnecessary, irrelevant traffic.
But do think twice before permanently taking down a page. If you’re not sure, you can always set up a redirect and still see some traffic. However, if you do decide to completely kill a page, be on the lookout for links that link out to the soon-to-be-deleted page that will break once the page’s removed.
503 Service Unavailable
The 503 Service Unavailable status code indicates that the website server is currently unavailable and, consequently, cannot process the incoming client request.
In the vast majority of cases, the 503 status code appears if the server is too busy, as in it’s exceeding the limit on the number of concurrent users, or if the server’s undergoing maintenance works.
It can also be used in other cases, for example, if:
- There’s a DDOS attack on the website,
- The website’s using a lot of scripts or external elements like widgets and images,
- It’s taking too long to pull the requested data from the database, or
- A lot of search bots or parsing softwares make simultaneous requests.
Ideally, the 503 page should contain a message that specifies the exact time when the visitor should come back, but this is rarely the case.
Last but not least, the 503 status code blocks search engines from indexing the site. Additionally, it signals to search engines that the site is poorly maintained because users can’t find what they’re looking for. Therefore, it’s important that such issues are solved as quickly as possible. Otherwise, it will affect your overall search rankings.
Setting up the 503 page via PHP
Here’s what the 503 status code looks like in PHP:
header(“HTTP/1.1 503 Service Temporarily Unavailable”);
header(“Status: 503 Service Temporarily Unavailable”);
Here you can read up about it in full detail.
Checking the server response with the Website Audit
To stay on top of everything that’s going on with your website, you must always keep an eye on your web pages and monitor their status codes. Sure, you can use the Live HTTP Headers extension for Chrome and the Index Coverage report in Google Search Console to view the status codes of your web pages, but it’s better if you spot and analyze them before the search engines do.
To do this, you can also make use of SE Ranking’s Website Audit.
In addition to being able to pinpoint and quickly identify website errors, the Website Audit tool also generates a list of suggestions that can help developers, content creators, and web designers do their job accurately.
By the way, you’re welcome to take advantage of the free trial to try out all of the features.
As you scroll through the audit report, you’ll see a detailed breakdown of everything that’s right and wrong with your website, including its SEO health, page, meta, content and link analysis. The best part is that you can easily find out if your site has any pages with an unexpected status code.
Just go to the Crawled Pages tab to analyze your page status codes, without any distractions — either directly in the platform or by exporting an XLS file:
You will still have to implement the changes manually, but finding them will no longer be a daunting task. Once you optimize the status codes of your web pages using the Website Audit, let Google know so that it can check and update them for everyone to see!
To help you out, we’ve put together a cheat sheet that outlines some HTTP status code SEO best practices: