HTTP Response Status Codes Explained

Are you a website owner, developer, or digital marketer looking to decode the mysteries of HTTP response status codes? If you answered “YES!,” it’s time to find a hobby! Just kidding.

HTTP (Hypertext Transfer Protocol) is used in the World Wide Web for transferring data between web browsers and web servers. It defines a set of rules and standards that govern how data is formatted, transmitted, and received over the internet.

In this blog, we'll try our best to unravel the purpose and significance of these codes in web communication. From common codes to their meanings, we'll delve into how these status codes impact website performance and user experience.  

Close-up view of computer code on a screen, highlighting HTML and CSS syntax for web development.


What are HTTP Status Codes?

HTTP status codes are three-digit codes that indicate the outcome of an API request. When you visit a website, your browser sends a request to the site's server, and the server then responds to the browser's request with the HTTP status code. Embedded within the API's response to the client, these codes furnish vital information, guiding the client on subsequent actions. A comprehensive grasp of these codes provides valuable insights.

The Complete Guide to HTTP Status Codes by Categories

HTTP status codes are categorized into five classes, each starting with a specific digit: 

1xx: Informational Responses

This class of status codes indicates that the request has been received and is being processed. They are primarily used to manage communication between the client and server during the early stages of a request-response cycle.

2xx: Success Responses

These codes signify that the request has been successfully processed and the requested action has been completed.  

3xx: Redirection Responses

3xx codes indicate that the client needs to take additional action to complete the request. They are often used when the requested resource has moved to a different location.

4xx: Client Error Responses

These codes indicate that the client has made an error in the request.  

5xx: Server Error Responses

5xx codes signify that the server has encountered an error while processing the request.  

1xx: Informational Responses

Here are some common 1xx codes and what they mean:

  • 100 Continue – The server has received the request and is expecting more data.
  • 101 Switching Protocols – The server is switching to a different protocol.
  • 103 Early Hints – The server may send a response with hints about the expected links of the final response while it is still preparing the response.

2xx: Successful Request

Here are some common 2xx codes and what they mean:

  • 200 OK – The request has been fulfilled, and the requested data is being sent.
  • 201 Created – A new resource has been created because of the request.
  • 202 Accepted – This response status code indicates that the request has been accepted for processing, but the processing has not been completed; in fact, processing may not have started yet.
  • 203 Non-Authoritative Information – The request was successful, but the payload has been modified by a transforming proxy from the origin server's 200 (OK) response.
  • 204 No Content – The success status response code indicates that the request has succeeded, and the client does not need to navigate away from its current page.

3xx: Redirection

Here are some common 3xx codes and what they mean:

  • 300 Multiple Choices – The redirect status response code indicates that the request has multiple possible responses. The user or user-agent should choose one of them, but there is no standardized way of doing so. As a result, this response code is very rarely used.
  • 301 Moved Permanently –The requested resource has been permanently moved to a new location.
  • 302 Found – The requested resource has been temporarily moved to a new location.
  • 303 See Other – The redirect status response code indicates that the redirects lead to another page, such as a confirmation page, a representation of a real-world object, or an upload-progress page, rather than the requested resource itself.
  • 304 Not Modified – This client redirection response code indicates that there is no need to retransmit the requested resources.
  • 307 Temporary Redirect – The redirect status response code indicates a temporary move of the requested resource to the URL provided in the location headers.
  • 308 Permanent Redirect – The redirect status response code indicates that the requested resource has been permanently moved to the URL specified in the location header.

4xx: Client Error 

Here are some common 4xx codes and their meaning:

  • 400 Bad Request – The request could not be understood by the server due to incorrect syntax.
  • 401 Unauthorized – The redirect status response code indicates that the requested resource has been permanently moved to the URL specified in the Location header.
  • 402 Payment Required – This status code is reserved for future use and was created to enable digital cash or payment systems. It indicates that the requested content is not available until the client makes a payment.
  • 403 Forbidden – This response status code indicates that the server understands the request but refuses to authorize it.
  • 404 Not Found – The requested resource could not be found on the server.
  • 405 Method Not Allowed - The server understands the request method, but the target resource does not support it.
  • 408 Request Timeout – This status code means that the server wants to shut down this unused connection. It is sent on an idle connection by some servers, even without any previous request by the client.
  • 409 Conflict – This response status code shows a conflict between the request and the current state of the resource.
  • 410 Gone – The client error response code indicates that access to the target resource is no longer available at the origin server and that this condition is likely to be permanent.
  • 414 URI Too Long – The response status code indicates that the client's requested URI is too long for the server to interpret.
  • 415 Unsupported Media Type – The client error response code indicates that the server refuses to accept the request due to an unsupported payload format.
  • 429 Too Many Requests – The response status code indicates that the user has exceeded the allowed number of requests within a specific time period, known as "rate limiting.”

5xx: Server Error

Here are some of the most common 5xx codes and what they mean:

  • 500 Internal Server Error – A general server error has occurred.
  • 501 Not Implemented – This server error response code means that the server does not support the functionality required to fulfill the request.
  • 502 Bad Gateway – The server error response code indicates that the server received an invalid response from the upstream server while acting as a gateway or proxy.
  • 503 Service Unavailable – The server is currently unable to handle the request due to temporary overload or maintenance.
  • 504 Gateway Timeout – This code indicates that the server, acting as a gateway or proxy, did not receive a timely response from the upstream server to complete the request.
  • 507 Insufficient Storage – The response status code is relevant in the context of the WebDAV protocol.
  • 508 Loop Detected – The server terminated an operation due to encountering an infinite loop while processing a request with "Depth: infinity." This status indicates a complete failure of the operation.
  • 510 Not Extended – If a client includes an extension declaration in a request, but the server does not support the described extensions, it will respond with a 510-status code.
  • 511 Network Authentication Required – This indicates that the client needs to authenticate to gain network access.

Unusual and Server Specific Status Codes

It’s important to note that there are some less common codes with some specific uses. One example is “418 I'm a Teapot.” The client error response code indicates that the server refuses to brew coffee because it is permanently a teapot. A combined coffee/tea pot that is temporarily out of coffee should instead return 503. This error is a reference to the Hyper Text Coffee Pot Control Protocol defined in April Fools' jokes in 1998 and 2014. “451 Unavailable for Legal Reasons” is another one. This response code indicates that the user requested a resource that is not available due to legal reasons, such as a web page for which a legal action has been issued, and it’s also reference to the Fahrenheit 451 novel.

There are some additional server codes through Microsoft's Internet Information Services (IIS), Apache, Nginx servers, and the Shopify platform. Internet Information Services (IIS) is a web server developed by Microsoft for use with Windows operating systems. It’s a powerful and versatile server that supports a wide range of features. Apache is a free and open-source web server that is widely used around the world, known for its reliability, security, and flexibility. Apache supports a wide range of features as well.  Nginx is a high-performance web server that is known for its efficiency and scalability, often used for high-traffic websites and applications. Finally, Shopify is a cloud-based e-commerce platform that allows businesses to create and manage online stores. 

Cloudflare's reverse proxy service expands the 5xx series of errors to provide more detailed information about the origin server's status. This allows website owners to better understand and troubleshoot issues with their servers.

The Most Important Status Codes for SEO and UX

UX design and SEO are essential components of modern web design and development, working together to create user-centric experiences and improve a website's visibility and success in search engine results. HTTP status codes can impact SEO by affecting the user experience and search engine crawlers' ability to access and index your website. For example, if a search engine encounters a 404 error (page not found) when trying to index a page, it may assume the page is no longer available and remove it from its index, which can lower your search rankings. 

Also, a 500 error or slow loading time can also harm SEO by negatively impacting the user experience and potentially causing search engines to lower your rankings. It's important to ensure that your website returns the correct HTTP status codes and promptly address any errors to ensure the best user experience and SEO performance.

How to Handle Client-Side Error Codes (4xx)

A common 4xx error is the dreaded “404 Not Found” code. This occurs when a client (usually a web browser) tries to access a resource (like a web page or file) that doesn't exist on the server.  To resolve 404 errors, you should double-check the URL, refresh the page, check the website's help section, or contact the website owner if the problem persists. 
Links that lead to a 404 page are often called broken or dead links. If it's unclear whether the unavailability is temporary or permanent, a 404-status code is typically used. If the requested resource is no longer available and it’s likely permanent, the HTTP “410 Gone” error code should be used. 

Remember, user-friendly error pages are not just about aesthetics; they play a crucial role in maintaining user engagement, building trust, and ensuring a positive user experience on your website.

Dealing with Server-Side Error Codes (5xx)

When it comes to identifying and fixing server-side issues (5xx errors), there are several ways to address these challenges:

  • Monitoring and Alerting: Implement robust monitoring and alert systems to quickly detect 5xx errors as they occur by using tools such as server log analysis, uptime monitoring services, and error tracking software to receive real-time alerts when server-side issues comes up.
  • Root Cause Analysis: Once a 5xx error is detected, conduct a thorough root cause analysis to pinpoint the exact source of the issue. This may involve examining server logs, tracing the sequence of requests, and analyzing any recent changes or deployments that could have triggered the error.
  • Performance Testing: Performance testing (load testing, stress testing) and capacity planning can help uncover weaknesses in your server setup and identify potential bottlenecks or resource limitations that could lead to 5xx errors. 
  • Code Review and Debugging: If the 5xx errors are from application code, perform comprehensive code reviews and debugging sessions to identify and rectify any bugs, exceptions, or inefficient code.
  • Scaling and Redundancy: Assess the scalability and redundancy of your server architecture to ensure it can handle fluctuating loads and unexpected traffic spikes. Consider implementing load balancing, auto-scaling, and redundant server configurations to mitigate the risk of 5xx errors during high-traffic periods.
  • Security Audit: Conduct a security audit to identify potential vulnerabilities or malicious activities that could result in 5xx errors, such as DDoS attacks, SQL injection, or other forms of cyber threats.

By employing these strategies, you can effectively identify and fix server-side issues (5xx errors) to maintain a stable and reliable web infrastructure for your users. A timely resolution of these issues is important for maintaining site reliability.

Redirection Best Practices

The main difference between 301 and 302 redirects lies in their intended purpose and impact on search engine optimization (SEO).  

A 301 redirect is a permanent redirect, indicating that the original URL has permanently moved to a new location. It’s used when a web page has been permanently moved or replaced with another page, and it informs search engines that the old URL should be replaced by the new one in their index. A 301 redirect transfers the SEO value (such as backlinks, authority, and ranking signals) from the old URL to the new one. Search engines interpret this redirect as a signal to pass the ranking power from the old page to the new one.

A 302 redirect is a temporary redirect, indicating that the original URL has temporarily moved to a new location. It’s used when a web page has temporarily moved, and the intention is to maintain the original URL's presence in search engine indexes. A 302 redirect does not transfer the SEO value to the new URL and search engines will continue to attribute the SEO value to the original URL.

Some best practices for redirects to maintain SEO value include:

  • Use 301 Redirects for Permanent Changes
  • Avoid Using 302 Redirects for Permanent Moves
  • Update Internal Links
  • Monitor Crawl Errors
  • Implement Hreflang (an HTML attribute used to specify the language and geographical targeting of a webpage) Tags

Tools and Resources for Monitoring HTTP Status Codes

There are some well-known tools for tracking and analyzing HTTP response codes available, including:

  • Google Search Console: Formerly known as Google Webmaster Tools, this free tool provided by Google allows webmasters to monitor their website's presence in Google search results.
  • Screaming Frog SEO Spider: This desktop program is widely used for website crawling and auditing. 
  • Pingdom: Pingdom offers website monitoring services, including the ability to track HTTP response codes and response times from various geographical locations. 
  • Dynatrace: This full-stack monitoring tool provides real-time insights into website performance, including the monitoring of HTTP response codes, server-side performance, and user experience metrics.
  • New Relic: This application offers performance monitoring and observability solutions that help track HTTP response codes, analyze server-side performance, and gain visibility into the behavior of web applications.

Regular monitoring of HTTP response codes can significantly improve a website's health and performance by detecting issues early, identifying slow-loading pages and bottlenecks, enhancing the user experience, positively impacting SEO, and enabling the proper allocation of resources to handle peak loads and traffic spikes effectively.'s Expertise in Managing Web Performance and SEO

It’s crucial for website owners, developers, and digital marketers to understand these codes and how they can impact SEO and the user experience. offers SEO strategy and consulting services to set websites up for success, and we create a blueprint based on an SEO audit and our team’s expertise to guide your website’s SEO tactics and set goals for tracking your strategy. In addition, we provide secure and reliable hosting that's monitored 24/7/365 by experienced team. We work to ensure your website always performs, even during a high traffic spike or a cyber-attack. Our hosting expertise includes over two decades of experience, and we’ve hosted websites during many high-profile events. We consider website performance optimization, SEO, and error resolution with all of our clients to ensure maximum efficiency and performance. 

For any web development and digital marketing needs you may have, we are here and would be happy to discuss our digital services and how your business can benefit from them.

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About Author

Shawn Griffin
Shawn has been with since 1999 in a variety of roles. Currently, Shawn is part of our digital marketing and content team. In addition to editing and producing written company pieces, he produces copy for clients and he also helps to produce our radio and TV spots. He wants to make sure everybody knows that it’s truly a collaborative effort – between many, including the people he’s worked for during the past 20+ years!

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