What is HTTP 421 Status Code (Misdirected Request)?

Reliqus Marketing

10 May 2024

HTTP Status Codes
By Ankit Bhatia
Founder & CEO

In today’s digital landscape, the performance of your website is crucial. HTTP status codes, like the 421 Error, play a significant role in web server communication but are often overlooked until problems arise. Known as “Misdirected Request,” this error can negatively impact your site’s user experience and SEO if not promptly addressed.

At Reliqus Consulting, we are experts in diagnosing and resolving such intricate web issues. This blog will explain an HTTP 421 status code error, how it affects your website, and the steps you can take to resolve and prevent it, ensuring your online presence remains strong.

What is HTTP 421 Error?

The HTTP 421 status code, defined as “Misdirected Request,” is a server-side error that may not be as familiar as like the 404 “Not Found” or the 500 “Internal Server Error.”

This error occurs when the server understands the request but cannot process it due to a condition that may be considered temporary. Specifically, it means the request was directed at a server that cannot respond. This situation can arise when a connection is reused or an alternative service is selected ALT-SVC, potentially leading to misdirecting requests. 

Clients encountering a 421 error can attempt to resend their request via a different connection. Importantly, this advice applies to all request methods, regardless of their idempotency. 

It is crucial to note that proxies should not generate this status code. Furthermore, responses with a 421 status code are considered cacheable by default, barring specific method definitions or explicit cache controls that suggest otherwise.

Connection Reuse: RFC7540 Section 9.1.1

Calculating Heuristic Freshness: RFC7234 Section 4.2.2

421 Misdirected Request Source: RFC7540 Section 9.1.2

To explore more about these and other HTTP status codes, check out our detailed series on HTTP status codes. Now, let’s dive deeper into what the HTTP 421 error entails and how it can be addressed.

📌Note: Website owners need to understand that search engines, like Google, will not index URLs that return a 421 Misdirected Request response status. If URLs previously indexed start returning this HTTP status code, they will be removed from search results.

421 HTTP Response Status Code References

Rails HTTP Status Symbol :misdirected_request

.NET HttpStatusCode.MisdirectedRequest

Rust http::StatusCode::MISDIRECTED_REQUEST

Go http.StatusMisdirectedRequest

Symfony Response::HTTP_MISDIRECTED_REQUEST

Python3.5+ http.HTTPStatus.MISDIRECTED_REQUEST

Apache HttpComponents Core org.apache.hc.core5.http.HttpStatus.SC_MISDIRECTED_REQUEST

Angular @angular/common/http/HttpStatusCode.MisdirectedRequest

HTTP 421 Status Code Example

The server responds to the client’s request with the 421 Misdirected Request error message because it received a request that wasn’t intended for it.

Request

GET /tech-news HTTP/2

Host: www.example.re

Response

HTTP/2 421 Misdirected Request

How to Use 421 HTTP Status Codes for a Website?

To effectively leverage the HTTP 421 Status Code for website optimization, backend tools for the web server should be implemented. This status code plays a pivotal role in scaling, efficiency, and accurately responding to client requests by signaling the need for correct request routing. 

Utilizing the “header” function in programming languages such as JavaScript, Python, Ruby, PHP, Java, C#.Net, Perl, C++, Scala, and Kotlin allows for explicitly sending this status code. 

Additionally, incorporating Server Name Indication (SNI) enhances SSL protocols by including the hostname within the initial SSL handshake message. This ensures the server selects the proper named virtual host for the request, establishing the necessary connection from the outset.

How to Check HTTP 421 Misdirected Request?

To check for a 421 HTTP Status Code, utilize the web browser network tab and developer tools for every resource the client uses. This feature allows you to monitor your browser’s network requests as you interact with a website. 

Which HTTP Method is used with the HTTP 421 Status Code?

The HTTP method used with the HTTP Status Code 421 is the GET method. This status code indicates that the request was misdirected to a server incapable of responding, often due to connection issues or invalid syntax structure. 

Unlike the 400 HTTP Status Codes that signify invalid syntax, the 421 error code results from a connection refusal

What are the Related HTTP Response Headers with 421 HTTP Status Codes?

Related HTTP Response Headers with HTTP 421 Status Code include various client and server error responses that provide additional context about the nature of the error encountered. Notably:

  • 414 URI Too Long HTTP Status Code: This client error response indicates that the client’s requested URI is longer than the server can interpret. The excessive length typically hinders processing and can be a security risk, prompting this error response.
  • 418 I’m a teapot HTTP Status Code: As a humorous client error response, this code signifies that the server refuses to brew coffee because it is, in fact, a teapot. This error is a nod to an April Fools joke but is recognized in protocol documentation.

What is the Browser Compatibility of the HTTP 421 Status Code?

The 421 HTTP Status Code is universally compatible with all modern web browsers. Specific browsers that support the 421 HTTP Response Status Code include Chrome, Edge, Firefox, Internet Explorer, Opera, Safari, and Webview Android.

This broad compatibility ensures that the implications of a 421 error can be understood and addressed across different platforms and devices, contributing to a more consistent web experience for users.

Common Causes of HTTP 421 Error Code

While the HTTP 421 Misdirected Request status code is not as frequently encountered as other status codes, it signals specific issues regarding how servers’ requests are directed and processed.

This status code arises under particular circumstances that can disrupt the normal flow of HTTP requests.

  1. HTTP/2 Server Configuration: Sometimes, a server refuses to process a request because it’s directed at a server that is not capable or willing to generate a response. This refusal often ties back to misconfigurations in servers operating under HTTP/2 protocols, which are more stringent about request routing.
  2. Server is Not Configured for the Requested Address: This occurs when the server cannot generate responses for the scheme and authority included in the request URI. The server doesn’t recognize the destination or lacks the appropriate configuration to respond appropriately.
  3. TLS (SSL) Certificate Misconfiguration: In environments leveraging SNI (Server Name Indication) to host multiple domains on a single IP address, any discrepancy or error in TLS certificates can trigger a 421 error. The server detects a mismatch and thus deems the request misdirected.
  4. Load Balancers or Reverse Proxies: Misconfigurations or incorrect routing within systems employing load balancers or reverse proxies can cause requests to be sent to the wrong backend server. The backend server, in turn, identifies the request as intended for another server, resulting in an HTTP 421 error.
  5. HTTP/2 Connection Reuse: The HTTP/2 protocol allows the reuse of connections for different requests across domains that resolve to the same IP address. However, if a server policy restricts specific requests from being processed over a reused connection due to the requested host’s specificities, it may return a 421 response. This mechanism aims to streamline connections but can inadvertently cause misdirected requests if not managed correctly.

Best Practices for Using HTTP 421 Status Code

When employing the HTTP 421 Misdirected Request status code, adhering to a set of best practices can significantly reduce the likelihood of its occurrence and ensure smoother server operations.

Consider the following recommendations:

  1. Proper Configuration: It’s crucial to ensure your server is accurately configured to handle requests directed at the intended host. This involves checking server settings and making necessary adjustments to accommodate all valid request URIs, especially in environments where multiple domains are hosted.
  2. Monitor DNS Settings: Regular and timely updating of DNS settings is essential. Accurate DNS configurations help incorrectly direct requests to the intended server, minimizing the chances of a request being misdirected.
  3. Use SSL/TLS Securely: Proper implementation of SSL/TLS certificates and configurations is non-negotiable. Errors in these areas can lead to misinterpretations of request destinations, thus triggering a 421 error. Ensure your SSL/TLS setup is faultless and routinely reviewed for discrepancies.
  4. Load Balancer Configuration: Precise configuration is critical for setups utilizing load balancers or reverse proxies. Ensure these intermediaries are set up to route requests to the correct backend servers based on the request’s intended destination and server capabilities. This precision will help avoid misdirection and the subsequent 421 status code errors.

Identifying HTTP 421 Status Codes Error

Identifying 421 status codes requires a strategic approach to catch and correct these errors quickly. Here are some methods to help in their detection:

  1. Server Logs: Start with the server logs, which are a comprehensive record of all requests processed by your server, including the status codes returned. These logs can help pinpoint when and why a 421 HTTP error occurred.
  2. Website Crawlers: Tools like Screaming Frog SEO Spider, DeepCrawl, or Botify offer an in-depth analysis of your website by crawling each URL. They can provide detailed reports on the status codes encountered, making identifying pages generating a 421 code error easier.
  3. Google Search Console: Utilizing Google Search Console is crucial for any website owner. It helps monitor your site’s presence in Google Search results and spot issues like HTTP 421 errors that could affect your site’s indexing.
  4. Chrome Developer Tools: Chrome Developer Tools can be invaluable for real-time analysis. You can see each request’s status codes by inspecting the Network tab while your webpage loads. This method is beneficial for identifying misdirected requests leading to 421 errors on the fly.

HTTP 421 Status Code Impact on Business and SEO

A 421 status code can significantly impact a website’s SEO performance if not managed appropriately. Search engines prioritize user experience, valuing factors like speed and the consistent availability of content. 

Here’s how 421 status error codes can detrimentally affect SEO:

  • Website Availability: Frequent 421 errors signal to search engines that a site might not be reliably accessible, which can lead to a decreased crawl rate. Over time, this diminished visibility can result in lower search result rankings, as search engines aim to direct users to available content.
  • User Experience: Encountering a 421 error can disrupt the browsing experience, proving frustrating for users. This frustration may increase the site’s bounce rate, as visitors will likely leave rather than wait for the issue to be resolved. Search engines often interpret A high bounce rate as a sign of poor user experience, negatively influencing SEO rankings.
  • Website Speed: Though 421 errors are not directly related to site speed, the underlying issues causing these errors, such as server misconfiguration or improper connection management, can lead to slow-loading of pages. Slow page loads adversely affect a site’s ranking in search engine results pages (SERPs), as speed is a crucial factor in SEO.

For businesses that rely heavily on their online presence for sales and conversions, server errors can directly impact revenue. The inability to complete transactions or access critical information can halt operations and lead to direct financial loss.

Reliqus Consulting’s Approach

We understand that minimizing downtime and optimizing server response is paramount. Our expertise in diagnosing and resolving server errors ensures that your digital infrastructure supports, rather than hinders, your business objectives. 

We employ a proactive approach to server management, ensuring that potential issues are addressed before they impact your users or SEO performance.

How to Handle 421 Code Errors in JavaScript?

Handling a 421 error in JavaScript is crucial for improving the user experience on your website. A straightforward way to manage this error involves using the JavaScript fetch API to send requests to an API endpoint. 

Here’s a basic example:

fetch(‘<https://example.com/api/resource>’)

  .then(response => {

    if (!response.ok) {

      throw new Error(‘Request failed: ‘ + response.status);

    }

    return response.json();

  })

  .catch(error => {

    console.error(‘Error:’, error);

    // Handle the error appropriately, such as displaying a message to the user

  });

This code snippet demonstrates how to check if the response status is outside the successful range (200-299) and throws an Error object. Errors, including a 421 status, are then handled in the `catch` block, allowing for appropriate user notification or other error management strategies.

How do you test the 421 Status Code on Postman?

Testing an HTTP 421 status code in Postman is straightforward. Follow these simple steps:

  1. Open Postman and create a new request.
  2. Enter the endpoint URL you wish to test into the request URL field.
  3. Send the request by clicking the “Send” button.
  4. Check the response status code in the Postman response section.

If the response status code is 421, it indicates that the request was misdirected. This means the server recognized the request but could not process it due to a configuration or routing error.

How do you test the Status 421 Code in the Chrome DevTools browser?

To test for an HTTP 421 Status Code using Chrome DevTools, follow these steps:

  1. Open Google Chrome and navigate to the webpage you wish to test.
  2. Launch DevTools by pressing F12 or right-clicking on the page and selecting “Inspect.”
  3. Click on the “Network” tab within DevTools.
  4. Reload the webpage to capture the network requests.
  5. Look through the list of network requests for any that display a 421 status code.
  6. Clicking on a request with a 421 status code will allow you to examine the details of both the request and the response within DevTools.

Conclusion

HTTP 421 errors, while challenging, are manageable with the right support and strategies in place. Reliqus Consulting ensures that your digital operations are maintained and continuously improved, driving better business outcomes and enhancing user satisfaction.

You gain more than just a service provider—a partner dedicated to your continuous digital success.

Take the next step towards a more stable and efficient online presence. Reach out to us today, and let us help you turn technical obstacles into stepping stones for growth and excellence.

Frequently Asked Questions About HTTP 421

How can I prevent 421 errors on my server?

To prevent 421 errors, ensure your server is not overwhelmed with requests and correctly manages connection limits and timeouts.

Can a misconfigured firewall cause a 421 error?

A misconfigured firewall can cause a 421 error by improperly limiting or blocking otherwise valid connections.

Does server misconfiguration always cause a 421 error?

No, a 421 error is not always caused by server misconfiguration; it can also result from high traffic volumes or client-side issues.

How do I troubleshoot a 421 error?

Troubleshoot a 421 error by checking server logs, reviewing server settings related to connection management, and verifying firewall and network configurations.

Can I customize the error message for a 421 error?

You can customize the message for a 421 error if your server software supports error message customization, typically through configuration files or server-side scripting.

What is 421 misdirected request Safari?

A 421 Misdirected Request in Safari indicates that the browser received an unexpected response from the server, possibly due to an HTTP/2 protocol issue or misconfigured server settings regarding host and IP address assignments.

What is 421 misdirected request Nginx?

In Nginx, a 421 Misdirected Request error occurs when the server configuration cannot correctly handle the HTTP/2 connection to the requested host, often requiring a review of server blocks or SSL/TLS configurations.

What is HTTP/1.1 421 misdirected request PRTG?

The HTTP/1.1 421 Misdirected Request error in PRTG indicates a problem where the monitoring request was sent to an incorrect server or service, which could be due to issues in DNS, SSL/TLS certificates, or server configuration in a network using HTTP/2.

Ankit Bhatia

Founder & CEO at Reliqus

With 12+ years of experience building a web presence for 300+ businesses, Ankit understands how businesses can use technology to increase revenue.

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