What is a 4XX Error? A Guide to 4XX HTTP Status Codes

If you are new to the internet and have just started browsing online content, you will likely encounter various types of HTTP errors, with 4XX error types being quite common. These messages are displayed when there’s a problem communicating between a web server and a browser.

These 4XX errors can be confusing and intimidating for any individual. Therefore, it is natural to wonder whether something has gone wrong on your side or if there is a problem with your system.

The 4XX errors, in particular, indicate client-side errors, meaning the problem is caused by the user or client device rather than the server. In this article, we’ll explore what 4XX errors are, their causes, types, and how to avoid them.

So let us get started then!

What is a 4XX Error?

The 4XX error code means that there’s a problem with the client’s request i.e. the error is caused by the user or the client device rather than the server.

The client-side error response range is from 400 to 499. These errors are different from 5xx errors, which indicate a server-side error.

These errors can occur due to a variety of reasons and can have a negative impact on SEO as well as user experience

For example, a 404 error message means that the client requested a page that doesn’t exist on the server.

Read: 🚩 A Complete Guide to Understanding HTTP Status Codes 

What are the common causes of 4XX errors?

There are several reasons why 4xx errors occur, including:

  • Incorrect URLs or links: This happens when a user tries to access a page with a wrong URL or a broken link.
  • Expired or invalid sessions or cookies: When a user tries to access a website with an expired or invalid session, they’ll encounter a 4xx error.
  • User authentication issues: When a user tries to access a page without the proper authentication or credentials, they’ll receive a 4xx error.
  • Server or website configuration errors: These errors happen when there’s an issue with the server or website configuration, such as the web server is down, the server is overloaded, or there’s a misconfiguration.

How 4xx errors are different from 5xx errors?

4xx errors and 5xx errors are HTTP status codes that indicate different types of errors that can occur when a user tries to access a web page. The main difference between these two categories of errors is their origin or source.

4xx errors are client-side errors, which means that the problem originates from the user’s side, such as a mistyped URL or an outdated cached version of the page. Some common examples of 4xx errors include “404 Not Found” and “403 Forbidden”.

On the other hand, 5xx errors are server-side errors, which means that the problem originates from the server hosting the website. These errors are typically caused by issues such as server overload, configuration problems, or coding errors.

Some common examples of 5xx errors include “500 Internal Server Error” and “503 Service Unavailable“.

In short, 4xx errors indicate client-side issues while 5xx errors indicate server-side issues.

Types of 4xx Error with their meaning and Fixes

There are several different types of 4XX errors, each with its own unique meaning and potential solutions. Here is a list of some of the most common types of 4xx errors you might encounter on a daily basis.

400 Bad Request

error 400
Error 400

This error occurs when the server cannot understand the request due to malformed syntax. It indicates that there is a syntax error in the request made by the user agent. This error can Cause due to,

  • Typed incorrect URL or used some characters that are not allowed.
  • Uploading a large file that exceeds the threshold limit.
  • Cookies and cache memory that have been stored in the browser get corrupted.

To fix this error, All you have to do is,

  • Carefully type the URL in the address bar and recheck the URL for any typo errors.
  • Clear your Browser History, Cookies, and cache from your browser as well as DNS cache.
  • Disable or deactivate Extensions that you installed on your browser.

401 Unauthorized

error 401
Error 401

This error occurs when the user is not authenticated or has failed to provide proper authentication. It indicates the request made is Unauthorized and it needs user authentication. The response from the server along with this status code includes a WWW-Authenticate header field which contains an authentication challenge to be fulfilled by the user agent. 


  • Incorrect login credentials
  • Expired login credentials
  • Missing authentication token
  • Incorrect authentication method

To fix this 401 Unauthorized error you have to do is,

  • Check login credentials
  • Refresh authentication token
  • Check authentication method
  • Provide helpful error messages

402 Status Code –Payment Required

error 402
Error 402

HTTP 402 is a status code that indicates payment is required to access the requested resource. It is a nonstandard status code, that is specially reserved for future use.


  • Payment errors
  • Internal troubleshooting
  • A failed attempt to access resources that required payment
  • An issue with the payment Gateway
  • Incorrect payment details
  • Technical difficulties with the website


  • Check payment details
  • Use a different payment method
  • Clear cache and cookies
  • Contact customer support
  • Update Browser and payment system
  • Check documentation

Read: 🚩 How to Fix HTTP 402 “Payment Required” Error?

403 Forbidden

error 403
Error 403

Error 403 refers to a “Forbidden” error, which occurs when a user attempts to access a web page or resource that they do not have permission to access.


  • Incorrect file Permissions
  • Misconfigured Server Settings
  • URL or directory structure
  • Server and Firewall issue
  • Server and Firewall issues
  • Browser issues
  • Accessing the wrong web location


  • Check Missing Core Files and Theme Files
  • Check the .htaccess file configuration
  • Check file and folder permissions
  • Check Plugins
  • Clear Browser Cache and Cookies
  • Try to fix issues from your Chrome Browser
  • Deactivate Browser Extensions
  • Check Firewall Settings

Read: 🚩 How to Fix WordPress 403 Forbidden Error? [9 Quick Fixes] & How to Fix 403 Forbidden NGINX Error on Your Site?

404 Not Found

error 404
Error 404

The 404 Not Found error is the standard response code of the web server, which occurs when the requested resource cannot be found on the server.


  • Invalid URL
  • Problem with DNS settings
  • Corrupt Browser Cache
  • WordPress Compatibility Issues
  • Server Issues
  • Incorrect Redirect


  • Reset Permalinks
  • Disable themes and Plugins
  • Restore .htaccess File

Read: 🚩 How to Fix 404 Not Found Error for WordPress Site & Android?

408 Request Timeout

error 408
Error 408

It is also known as a ‘Request Timeout’ error. It occurs when the server is waiting for the request, but the client is not able to send a request within a certain time frame.


  • Network Issues
  • Server Overload
  • Firewall and Security Settings


  • Check your network connectivity
  • Check your Firewall and Security Settings
  • Contact the website and Server Admin
  • Try again Later

List of Other Uncommon 4XX Errors

This series of status codes signify that there is some error in the requested process at the user end and a new request is to be made after rectification of the request. 

  • 405 Method Not Allowed – The requested HTTP method is not allowed for the requested resource.
  • 406 – This status code is returned when the requested resource is only capable of generating content not acceptable according to the Accept headers sent in the request. 
  • 409 – It indicates that there is a conflict in the request made. 
  • 410 Gone – The requested resource is no longer available on the server and there is no forwarding address.
  • 411 – It means that the user agent needs to specify the content length along with the request in order to be processed by the server. 
  • 413 Payload Too Large – The server cannot process the request because the payload is too large. 
  • 414 – It indicates that the requested URI is too long for the server to process. 
  • 415 Unsupported Media Type – The server cannot process the request because the media type is unsupported.
  • 429 Too Many Requests – The user has sent too many requests in a given amount of time, and the server is rate-limiting them.
  • 444 – It is an Nginx HTTP server extension, known as the ‘No Response’ status code returned when the server returns no information and is used to curb malware. 
  • 451 – It refers to denial of access due to Legal Reasons, imposed by censorship or a government mandate. 
  • 499 – It indicates that the connection is being closed by the client while the server is processing the request, so the server cannot return the HTTP header back to the client. 

Note: It’s worth noting that some websites may use additional custom 4xx errors, but these are the most common ones that you may encounter.

Impact of 4XX Errors on SEO

As we have already mentioned so many times, 4XX errors are client-side errors that occur when a user requests a webpage that the server cannot find or access.

These errors can have a negative effect on SEO (Search Engine Optimization) because they prevent search engines from accessing and indexing your website’s pages, resulting in decreased visibility and lower rankings in search engine results pages (SERPs).

Here are some of the ways in which 4XX errors can harm your website’s SEO:

  • Decreased crawl ability: When search engine bots encounter 4XX errors while crawling your website, they may stop crawling or indexing your pages. This can lead to decreased crawl ability and indexability, resulting in lower rankings in SERPs.
  • Broken links: If your website has broken links due to 4XX errors, it can harm the user experience, leading to a higher bounce rate and lower engagement metrics. This can negatively impact your website’s SEO as search engines prioritize user experience and engagement.
  • Loss of link equity: If you have internal or external links pointing to pages that return 4XX errors, it can result in a loss of link equity. This means that the authority and value of those links are not being passed onto your website, resulting in lower rankings in SERPs.
  • Negative user experience: 4XX errors can harm the user experience, leading to frustration and a higher likelihood of users leaving your website. This can result in decreased engagement metrics, such as time on site and pages per session, which can negatively impact your website’s SEO.

To avoid these negative effects on SEO, it’s essential to monitor and fix 4XX errors promptly. You can use tools like Google Search Console to identify and fix these errors, such as redirecting broken links, fixing incorrect URLs, or updating your sitemap. By addressing 4XX errors, you can improve your website’s crawl ability, user experience, and overall SEO performance.

How to Avoid 4xx Errors?

To avoid and fix 4xx errors, You can take several steps such as,

  • Check and correct errors in URLs and links
  • Verify user authentication and permissions
  • Update server and website configurations as needed
  • Use redirects or custom error pages
  • Monitor website traffic on a regular basis to identify errors and address recurring issues.


Addressing 4xx errors is essential for improving not only the user experience but also for maintaining a positive SEO ranking. You definitely don’t want to mess with Google’s algorithm, which always seeks to deliver the best user experience and content possible.

Therefore, by understanding the causes and types of 4xx errors, you must take the necessary steps to avoid them happening in the future and create a more user-friendly and reliable website.

Apart from all of the above, if you have any tips or suggestions regarding the 4xx Error that we have missed in this post, or would like to share your experience about the same, do let us know in the comment section below.

Frequently Asked Questions

What are 4xx or 5xx errors?

4xx and 5xx errors are HTTP status codes that indicate the status of a client’s request to a server. 4xx errors indicate client-side errors while 5xx errors indicate server-side errors.

What does received a 4xx error mean on duolingo?

If you receive a 4xx error on Duolingo, it means that there is an issue with the client side of your request to the Duolingo server. This could be due to a variety of reasons, such as a mistyped URL, an incorrect login credential, or a connectivity problem.

What is an example of 4XX errors?

An example of a 4xx error is the “404 Not Found” error, which indicates that the requested resource or web page could not be found on the server. Other examples of 4xx errors include “401 Unauthorized”, “403 Forbidden”, and “400 Bad Request”. These errors are typically caused by client-side issues, such as incorrect authentication credentials, insufficient permissions, or mistyped URLs.

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