HTTP 510 Response Status Code Guide: What is it, Usage, Methods

Jun 20 2024 by Oskay Günaçar

What is HTTP 510 Status Code?

The HTTP 510 Status Code, "Not Extended," is a server response status code indicating that the server requires further extensions to fulfill the request. This status code is used when additional extensions are needed for the server to process the request correctly.

It is often seen in cases where the request lacks some necessary information or capabilities that the server requires to complete the operation.

In essence, the 510 status code suggests that the client needs to provide more information or use different extensions to allow the server to handle the request successfully. This status code is defined in RFC 2774, which specifies the "HTTP Extension Framework" for handling such scenarios.

Here's a simplified example to understand its context:

  • Scenario: A client sends a request to a server, but the server requires additional extensions (such as certain headers or parameters) to process the request.
  • Server Response: The server responds with a 510 Not Extended status code, indicating that it needs more information to fulfill the request.

Clients encountering this status code should review the server's requirements and adjust their request accordingly to include the necessary extensions.

Common Causes of HTTP 510 Status Code

The HTTP 510 Status Code, "Not Extended," is relatively uncommon but can occur in specific situations where the server requires additional information or extensions to process the request. Here are some common causes:

  1. Missing Extensions:

    The client request lacks the necessary extensions that the server needs to handle the request. These extensions might include specific headers, parameters, or other data elements.
  2. Unsupported Request Features:

    The server identifies that the request is using features that are not supported or requires additional capabilities that the server cannot handle without further extensions.
  3. Incomplete Implementation:

    The server might be configured to require certain extensions for particular operations, and if the client does not include these, the server responds with a 510 status code.
  4. API Changes:

    In the context of APIs, if the server-side API has been updated to require additional parameters or headers that the client is unaware of, the client might receive a 510 status code.
  5. Custom Server Requirements:

    The server has custom requirements that are not part of the standard HTTP protocol, necessitating additional information or extensions from the client to process the request.

Importance of HTTP 510 Status Code in SEO

The HTTP 510 Status Code, "Not Extended," is generally not directly related to SEO (Search Engine Optimization) because it indicates an issue with the server requiring additional extensions to process a request. However, there are indirect ways in which encountering a 510 status code can impact SEO efforts:

1. Crawling and Indexing Issues:

  • Search Engine Bots: When search engine bots (like Googlebot) crawl your website and encounter a 510 status code, it indicates that the server cannot process the request due to missing extensions. This can prevent search engines from properly crawling and indexing your site.
  • Reduced Crawl Efficiency: Frequent 510 errors can reduce the efficiency of search engine bots, leading to incomplete indexing of your site content.

2. User Experience:

  • Access Problems: Users encountering a 510 status code might be unable to access certain parts of your website, leading to a poor user experience.
  • Bounce Rates: High bounce rates due to inaccessible content can negatively impact your SEO, as search engines consider user behavior metrics in their ranking algorithms.

3. Site Health and Performance:

  • Server Configuration: A 510 status code may indicate that your server configuration requires improvement. Properly configured servers are critical for maintaining a healthy website.
  • Performance Signals: A well-performing website is a positive signal to search engines. Repeated 510 errors might suggest underlying issues that need to be addressed to improve overall site performance.

4. Reputation and Trust:

  • Consistency: Consistent server issues, including 510 errors, can harm your site's reputation with both users and search engines.
  • Reliability: Reliable websites are favored by search engines. Addressing server issues promptly ensures that your site is perceived as reliable and trustworthy.

How to Mitigate the Impact of HTTP 510 on SEO

Monitor Server Logs

Regularly check your server logs for any occurrences of 510 status codes. Identifying and understanding the causes of these errors helps in proactively addressing issues before they impact SEO. Keeping an eye on server logs allows you to detect patterns and recurring issues that need attention.

Ensure Complete Requests

Make sure all client requests to the server are complete and include the necessary extensions or headers required by the server. This ensures that the server can process requests correctly, preventing the occurrence of 510 status codes.

Improve Server Configuration

Work with your server administrators or hosting provider to ensure that your server is properly configured to handle all requests. Proper server configuration is critical in preventing errors and maintaining a seamless user experience.

Communicate Requirements

Clearly document any server or API requirements so that clients, including search engine bots, can make fully compliant requests. Providing comprehensive documentation helps developers and other stakeholders understand the necessary extensions or headers required for the server to process requests.

Test Regularly

Regularly test your site for issues that could lead to 510 errors. This includes checking for proper implementation of all required features and extensions. Conducting regular tests ensures that your site remains accessible and functional, which is crucial for maintaining good SEO.

How to Fix the HTTP 510 Error From the Website?

Fixing the HTTP 510 error on your website involves several steps to ensure that your server can process requests correctly. Here’s a comprehensive guide:

Understand the Cause

The first step is to identify why the HTTP 510 error is occurring. This error indicates that the server requires additional extensions or information to fulfill the request. Check your server logs to pinpoint the exact cause.

Update Client Requests

Ensure that all client requests to the server include the necessary extensions or headers. This might involve updating the client-side code to comply with the server’s requirements.

Review and Implement Necessary Extensions

Identify the specific extensions or features that the server requires and ensure they are implemented correctly. This may involve:

  • Adding necessary headers to the HTTP requests.
  • Including required parameters in API calls.
  • Ensuring that all mandatory fields are filled out in forms or requests.

Check Server Configuration

Review your server configuration to ensure it is set up to handle the requests appropriately. This might involve:

  • Updating server software to the latest version.
  • Configuring server settings to accept the required extensions.
  • Ensuring that the server’s extension framework is properly implemented and enabled.

Update Documentation

If the server requires specific extensions or headers, ensure that this information is clearly documented. This helps developers and clients understand what is needed to make successful requests.

Test Your Fixes

After making changes, thoroughly test your website to ensure that the HTTP 510 error is resolved. This includes:

  • Testing various requests that previously caused the 510 error.
  • Using tools like Postman to manually check API requests.
  • Ensuring that automated tests cover scenarios that involve the necessary extensions.

Monitor Server Logs

Continue to monitor your server logs even after fixing the issue to ensure that the 510 errors do not reoccur. Regular monitoring helps in quickly identifying and addressing any new issues that arise.

Communicate with Your Hosting Provider

If you are unable to resolve the 510 error on your own, contact your hosting provider for assistance. They can provide insights and support in configuring the server correctly and addressing any underlying issues.

Implement Error Handling

Add proper error handling in your application to gracefully manage cases where the server requires additional extensions. This can include:

  • Displaying user-friendly error messages.
  • Logging detailed error information for debugging.
  • Retrying requests with the required extensions automatically.

By following these steps, you can effectively fix the HTTP 510 error on your website, ensuring that your server processes requests correctly and maintaining a seamless user experience.

What is the Browser Compatibility of HTTP 510 Status Code?

The HTTP 510 Status Code, "Not Extended," is a relatively uncommon status code that is not widely supported by all browsers. Here’s a breakdown of its compatibility with major browsers:

Browser Compatibility

Google Chrome

  • Support: Limited
  • Details: Chrome generally handles common HTTP status codes well, but the 510 status code may not be explicitly handled. Chrome will display a generic error message if it encounters this status code.

Mozilla Firefox

  • Support: Limited
  • Details: Firefox, like Chrome, may not have specific handling for the 510 status code and will likely display a generic error page when encountering this error.

Microsoft Edge

  • Support: Limited
  • Details: Edge, based on Chromium, follows similar behavior to Chrome. It may display a generic error message for the 510 status code.


  • Support: Limited
  • Details: Safari does not have specific support for the 510 status code. Users will likely see a generic error page if this status code is encountered.


  • Support: Limited
  • Details: Opera, also based on Chromium, will exhibit behavior similar to Chrome and Edge, displaying a generic error message for the 510 status code.

Implications of Limited Support

Due to the limited support across major browsers, encountering a 510 status code will not trigger specific error handling mechanisms or messages tailored to this status code. Instead, users will see generic error pages that do not provide detailed information about the 510 error.


The HTTP 510 Status Code, "Not Extended," is an uncommon but important server response code that indicates the need for additional extensions or information to fulfill a request. While it may not be directly tied to SEO, its implications can indirectly affect your website's performance, user experience, and search engine indexing. By understanding the causes and implementing proactive measures—such as monitoring server logs, ensuring complete requests, improving server configuration, and providing clear documentation—you can mitigate the impact of this error.

Fixing the HTTP 510 error involves a systematic approach to reviewing and updating client requests, server configuration, and necessary extensions. Regular testing and monitoring are crucial to ensure the issue is resolved and does not reoccur. Additionally, understanding the browser compatibility limitations of the 510 status code helps in setting realistic expectations for handling this error across different user agents.

By addressing these issues comprehensively, you can maintain a seamless and efficient website, ultimately enhancing the user experience and supporting your SEO efforts. Keeping your server and client configurations in check ensures that your website remains reliable, accessible, and ready to handle all necessary extensions without errors.

Oskay Günaçar
Oskay Günaçar is a Technical SEO expert and backend developer. His main areas of interest are back-end programming, Python, Django, Go, semantic SEO, technical SEO. With more than 5 years of SEO experience, he has held SEO specialist positions at İkiler, Webtures, Boosmart, and companies, and has been involved in numerous projects as an outsourced expert. Through the TechSEOHub website, he aims to share the expertise and experience he has gained from managing and developing (SEO) processes for many successful and large websites in the industry, and to produce content for easy access to accurate and high-quality information.