From a user’s perspective, a 404 page is probably the most common 4xx error. Have you ever stumbled upon one in search results or on a website? 

It’s not the best experience, I know, but it’s how servers inform you that your desired web page doesn’t exist, and it’s unknown whether it will be accessible in the future. 

4xx error status codes mean there is an issue on your side (the client side) that must be properly addressed. It’s serious stuff because if you fail to remedy it, your website’s indexability and performance will suffer. 

The good news is that the problem can be easily detected and fixed. 

I’ve frequently dealt with 4xx errors as part of technical SEO audits throughout my entire SEO career, so you’re in good hands. 

In this article, I’ll explain the most common 4xx HTTP status codes, why they occur, what they mean, and how they impact your on-page and off-page SEO. On top of that, I’ll show you how to fix them.

Let’s get to it …

What Is a 4xx Error? 

A 4xx status code means there is an error on the client’s side. In other words, the server can’t return a destination URL for some reason. The last two digits of the HTTP status codes differ and explain why your website’s URL can’t be shown. 

For example, a 404, one of the well-known status codes, means “the page is not found,” and it’s unknown whether or not it will be accessible again. On the other hand, 410 means the page is permanently gone. 

Below, I’ll briefly explain the most common 4xx errors so you’ll know how to interpret them and whether you need to take any action (so they don’t wind up as an eyesore on your SEO report).

Common 4xx Error Codes to Learn 

Various 4xx status codes indicate errors on a client’s side. However, most of them, like the 402 response code, rarely occur. Therefore, below I’ll focus on the common ones you’ll likely encounter while working on your website or clients’ websites. 

If you don’t have time to read the entire article, I’ve summarized 4xx error codes in the table below.

4xx Status Code What It Means
400 Bad Request The server can’t understand a client’s request because it’s wrong. Check your code, request headers, URL parameters, and request body to identify and correct the issue causing the error.
401 Unauthorized Request A client tries to access a resource, such as a secure web page, without providing proper authentication credentials.
403 Forbidden The server understands the request but does not allow the client to access it, even with valid credentials.
404 Not Found The requested resource has been moved or deleted, and it’s unknown whether or not it will be available in the future.
410 Gone Unlike 404, this status code indicates that the requested resource is permanently gone.

400 Status Code: Bad Request

A “400 Bad Request” status code is a response from a server to indicate that the request sent by the client (your browser) is malformed or invalid. 

The server can’t understand or process the request because it doesn’t meet the server’s expectations or requirements.

This error may occur if the request has incorrect syntax, such as missing required headers, invalid HTTP methods, or improperly formatted URLs.

401 Status Code: Unauthorized Request

A “401 Unauthorized” status code indicates that the client making the request has not been authenticated or lacks the necessary access credentials. 

In other words, the server tells the client that it needs to provide valid credentials (username and password) to access the resource, but the credentials are either missing or invalid.

403 Status Code: Forbidden

Unlike a “401 Unauthorized” status code, which implies that the client may gain access by providing valid credentials, a “403 Forbidden” status code means the server understands the request but does not allow access, even with proper credentials.

If you encounter a “403 Forbidden” response while browsing a web application, you won’t get access to it, and there is no immediate action you can take to gain it. I recommend contacting the server provider to inquire about the specific access restrictions.

404 Status Code: Not Found

“404 Not Found” often occurs when a user wants to access a page that no longer exists, a URL is mistyped, or a resource has been moved or deleted (sometimes in an attempt to resolve a keyword cannibalization issue).

I’ve encountered this 4xx error many times when developers accidentally deleted live website pages or when content managers accidentally made mistakes while editing pages in WordPress. 

Unless you run site audits daily, it’s unlikely to discover this error immediately. However, it can seriously harm user experience. 

410 Status Code: Gone

A “410 Gone” status code indicates that the requested resource has been intentionally and permanently removed or deleted and will not be available again.

I’ve used the “410 Gone” status code before doing website migration from a subdomain to a subfolder. 

Some URLs were unnecessary, so we requested their temporary removal via Google Search Console and changed the status code to “410 Gone” to inform search engine bots that the pages were gone permanently.

418 Status Code: I’m a Teapot

I had to write about the 418 status code, although you should know up front that it was developed as an April Fool’s joke and has no practical application.

The server can return the “418 I’m a Teapot” error status code when a client requests to “brew coffee, yet it’s a teapot.” In other words, it’s a server’s response to an inappropriate request.

Although 418 can undoubtedly bring a smile to developers’ and users’ faces, it doesn’t have any practical usage compared to other 4xx error status codes. 

4xx Error Codes and Their Impact on SEO

Search engine bots regularly crawl your website pages and record their status codes to understand whether they are accessible and healthy. 

As you know, the “200 OK” status code means all good. Your web page has no issues and can be shown in search results. On the other hand, displaying 4xx error status codes over time can cause pages to drop from the Google index

Besides page removal from organic search results, 4xx errors can cause even more problems to your website, such as the following:

1. Decreased Crawlability

There is no point in wasting Googlebot’s crawl budget on broken pages. 

If search engine bots regularly encounter the same 4xx status code on a web page, they’ll decrease its crawlability. This means that the affected page won’t appear in organic search results, which will eventually cause a loss of organic website traffic.

2. Rankings Drop

If an essential page of your website returns a 4xx error by mistake, fix it immediately. 

According to Google, pages with 4xx HTTP status codes are unhelpful for users. Therefore, they’ll slowly lose their rankings in organic search results and eventually be excluded from the Google index. 

3. Bad Signals for Quality

Besides 4xx, how will Google understand that the web page is unhelpful for users? A high bounce rate and a small average session duration per user indicate poor web page quality. 

If users click on an outbound link in a blog post and land on a page with an error message, they’ll simply leave it. Sooner or later, Google will notice this behavior and exclude the page from the index. 

4. Negative User Experience

If users regularly encounter 404 pages on your website, it will negatively impact their on-page experience. This leads to higher bounce rates, lower engagement, and, ultimately, a lower SEO ranking. Search engines, like Google, favor websites that provide a positive user experience. 

5. Lost Backlinks

If external websites link to web pages that return 4xx errors, you risk losing valuable link juice. Backlinks are an important SEO factor, and if the pages they link to are no longer accessible, it will harm your website’s authority and rankings.

If you want to discover 404 pages other websites link to, I recommend running a backlink audit for your website. 

4xx Status Codes vs. 5xx Status Codes

There is another group of HTTP status codes that can be detrimental to your website’s SEO: 5xx server errors. 

Unlike 4xx status codes, 5xx errors don’t happen on the client’s side (your browser). It means you can’t fix them on your own. Instead, these are errors on the server’s side, which a server returns when it can’t carry out the request.

Just like a 4xx error, I’m pretty sure you’ve stumbled upon a server error before, but here are the most common 5xx errors that might occur on your website.

5xx Status Code What It Means
500 Internal Server Error Something has gone wrong on the server, but the server can’t provide more specific information about the error.
501 Not Implemented The server doesn’t understand the request or can’t fulfill it.
502 Bad Gateway One server that acts as a gateway in a chain of servers gets an invalid response from another server.
503 Service Unavailable The server is temporarily unable to handle the request. It is often used when a server is undergoing maintenance or experiencing high traffic and can’t respond to the request at the moment.
504 Gateway Timeout Similar to a 502 error, a 504 error happens when a server acting as a gateway does not get a timely response from the server it was routing to. It indicates a timeout in the communication between servers.

Why Are 5xx Errors Bad for Your SEO? 

Because they slow down your website’s crawling. This means in time Google will drop them from the index.

If your website has 5xx errors, you’ll find them in Semrush’s Site Audit report. I frequently use Semrush for various marketing needs, such as keyword research, SEO competitor analysis, or tech SEO audit. If you’re interested in learning more, take a look at my Semrush review.

Semrush Site Audit 5xx status code

How to Fix 4xx Error Codes

Fixing 4xx HTTP status codes is easy if you know how to do it. 

If your website or clients’ websites have many 4xx errors, I recommend adding them to the technical SEO KPIs list. 

I’ve tried many ways to discover 4xx errors, including Google Search Console, Semrush, Ahrefs, Screaming Frog, and cURL for HTTP requests. 

Here are the three easiest methods:

1. Find 4xx Error Codes

You can see all 4xx status code issues in the Page Indexing report if you have a verified Google Search Console account.

Google Search Console - why pages aren't indexed

Alternatively, I recommend using Semrush Site Audit. It’s a go-to solution if you manage clients’ websites or don’t have access to Google Search Console. 

If any issues are detected, you’ll find them in the Site Audit > Issues report.

Semrush Site Audit 4xx status codes

2. Replace or Remove Broken Links

I check my Google Search Console account daily to quickly discover critical issues on my website, especially if it’s an essential page in terms of traffic, rankings, or e-commerce value.

If a 404 error occurs due to a mistyped URL, the internal or external link will be broken. In this case, you can do the following:

  • Manually fix the URL if it’s an external link. 
  • For internal pages, manually fix the URL, if a proper web page exists, and set a 301 (permanent) redirect from the broken URL to the correct one.

If you intentionally want to exclude certain pages from organic search results, apply the “410 Gone” status code. In this case, you must remove all internal links pointing to this URL. Otherwise, users can accidentally stumble upon this page. 

3. Create Custom 404 Pages 

There is another way to handle the 404 error. 

If you don’t have a relevant page to redirect users, you should create a custom 404 page. This page helps users understand where they are on your website and encourages them to explore it further. 

Here is what a Semrush 404 page looks like. Even if users accidentally get lost, a call to action button redirects them to the home page.

Semrush: We got lost, go to homepage

4xx Error Remedies to Improve Your Website’s Technical SEO

Even though 4xx errors won’t break your website in the short term, the long-term consequences are detrimental, including decreased crawlability, exclusion from Google’s index, and loss of organic search traffic. 

That’s why it’s so important to keep an eye on the HTTP status codes and the overall health of your website using SEO tools like Semrush. 

Register for a 7-day free Semrush trial to find and fix all HTTP status codes.

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