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400 Status Codes


400 status codes are a category of HTTP response status codes that indicate client errors, meaning that the request made by the client (such as a web browser or search engine crawler) cannot be fulfilled due to an error on the client’s side. These codes typically indicate issues such as invalid URLs, missing pages, or unauthorized access attempts.

Example of how you can use 400 Status Codes

For instance, when a search engine crawler encounters a 404 Not Found status code while attempting to access a web page on a website, it understands that the requested page is missing or cannot be found. This status code can be used to identify and address broken links or missing content on a website, improving overall site quality and user experience.

Formula or Calculation

There is no specific formula for calculating 400 status codes, as they are predefined status codes defined by the HTTP protocol. When a client sends a request to a server (e.g., requesting a web page), the server processes the request and returns an appropriate 4xx status code if the request cannot be fulfilled due to client error.

Key Takeaways

  1. 400 status codes indicate client errors, such as invalid URLs, missing pages, or unauthorized access attempts.
  2. The most common 400 status code is 404 Not Found, which indicates that the requested resource could not be found on the server.
  3. Other 400 status codes include 401 Unauthorized, which indicates that access to the requested resource is restricted and requires authentication.
  4. Monitoring and addressing 4xx status codes is important for SEO, as they can negatively impact user experience and search engine crawling and indexing.
  5. Implementing proper error handling and redirection mechanisms can help mitigate 4xx status code issues and improve website usability and SEO performance.


What are the most common causes of 4xx status codes?

Common causes include broken links, invalid URLs, missing pages, expired content, and unauthorized access attempts.

How can I identify and fix 4xx status code issues on my website?

Use tools like Google Search Console or website crawlers to identify pages returning 4xx status codes. Then, fix the underlying issues, such as updating or removing broken links, resolving server errors, or implementing proper redirects.

What impact do 4xx status codes have on SEO?

4xx status codes can negatively impact SEO by affecting user experience, causing indexing issues, and potentially leading to decreased search engine rankings if they persist or affect important pages.

Is it normal to encounter some 4xx status codes on my website?

Occasional 4xx status codes may be normal, especially for large or frequently updated websites. However, it's essential to monitor and address them promptly to maintain a positive user experience and SEO performance.

How can I prevent 4xx status codes from occurring on my website?

Take proactive measures such as regularly checking for broken links, ensuring proper URL structure and redirections, setting up custom error pages, and implementing security measures to prevent unauthorized access attempts.

Are all 4xx status codes bad for SEO?

While some 4xx status codes like 404 Not Found can be detrimental to SEO if they affect important pages, others like 410 Gone (indicating permanently removed content) may be more acceptable if the content is genuinely no longer available.

What should I do if a page on my website returns a 404 Not Found status code?

If a page returns a 404 Not Found status code, investigate the cause, and either restore the missing content, redirect users to relevant pages, or provide a custom error page with helpful information and navigation options.

Can 4xx status codes affect website traffic and user engagement?

Yes, 4xx status codes can negatively impact website traffic and user engagement by causing frustration and confusion among visitors, leading to increased bounce rates and decreased time on site.

How can I monitor 4xx status code issues on my website?

Utilize tools like Google Search Console, website crawlers, and server log analysis to monitor 4xx status code occurrences, identify trends and patterns, and take corrective actions as needed.

Is it necessary to fix every 4xx status code on my website?

While it's important to address significant and recurring 4xx status code issues, not every occurrence may require immediate attention, especially if they are isolated incidents or affect less critical pages.

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