Definition, identification & 404 errors fixes

Are you familiar with the 400 Bad Request error? How many of them exist or what could be causing it? Can you identify it, and more importantly, do you know how to eliminate it?

As a Digital Marketing expert, one of your main concerns will be understanding the reason for a 4xx error occurrence, as it can impact the User Experience of your users and negatively affect SEO.

Within this short guide, I will explain to you:

  • What a 4xx error is;
  • What causes them;
  • How you can resolve them permanently.

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What is a 400 bad request error?

When you browse the web and land on a webpage, you have essentially sent a request to the website’s server, which responds with an “HTTP Status Code”.

A 400 Bad Request is an HTTP status code that occurs when the requested webpage cannot be reached.

It usually happens due to syntax errors in the web address, a page not found, or limited access rights, indicating that the server cannot process the request, thus returning an error code. Similarly, a 500 internal server error indicates an issue on the server side that prevents the website from functioning properly.

Depending on the browser you are using, 400 errors might appear differently. When browsing with Firefox and Safari, you usually see an empty page without a status code.

On the other hand, Chrome displays a generic message “This page isn’t working” along with a more specific error code instead of the desired content.

Therefore, make an effort to prevent one or more pages of your site from responding with a 400 Bad Request status code. Periodically check for any “broken links,” otherwise, your users won’t be able to find what they’re looking for.

As I mentioned earlier, apart from providing a poor user experience due to interrupted navigation, there’s a high chance that the user might leave the site.

Also, search engine spiders don’t like being interrupted while scanning your website. Therefore, you might be penalized with the subsequent loss of ranking and positioning in the search engine results page (SERP).

A piece of advice I’d like to give you is to try to turn the 400 Bad Request error into an opportunity by creating a customized 404 page that can guide the user exactly where they intended or hoped to land, thus avoiding site abandonment.


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What are HTTP 4xx client error status codes

The HTTP 4xx status codes indicate that a client-side error has occurred. Through their code, it is possible to understand what caused them to correct it.

There are many of them, here is the complete list in case you need it:

  • 400 Bad Request
  • 401 Unauthorized
  • 402 Payment Required
  • 403 Forbidden
  • 404 Not Found
  • 405 Method Not Allowed
  • 406 Not Acceptable
  • 407 Proxy Authentication Required
  • 408 Request Timeout
  • 409 Conflict
  • 410 Gone
  • 411 Length Required
  • 412 Precondition Failed
  • 413 Payload Too Large
  • 414 URI Too Long
  • 415 Unsupported Media Type
  • 416 Range Not Satisfiable
  • 417 Expectation Failed
  • 418 I’m a teapot
  • 420 Enhance Your Calm
  • 422 Unprocessable Entity
  • 423 Locked
  • 424 Failed Dependency
  • 425 Too Early
  • 426 Upgrade Required
  • 428 Precondition Required
  • 429 Too Many Requests
  • 431 Request Header Fields Too Large
  • 444 No Response
  • 449 Retry With
  • 450 Blocked by Windows Parental Controls
  • 451 Unavailable For Legal Reasons
  • 499 Client Closed Request

If you are curious and want to delve into the topic, know that there is an international organization called “The Internet Engineering Task Force” (IETF) that deals with promoting and developing internet standards.


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How to identify an HTTP status 4xx

There are various ways and tools to identify the 400 bad requests on your site, but what I want to show you today is the easiest, quickest, and also free method.

By using the Screaming Frog tool, it is possible to freely crawl websites up to a maximum of 500 URLs, more than enough for a small to medium-sized website.

With the following video, you will be able to identify them easily. If you encounter any difficulties, you can follow the steps listed below.

  1. Download the Screaming Frog tool here.
  2. Run a site crawl after opening Screaming Frog, type or copy your site’s URL into the “Enter URL to spider” box, and click Start.
  3. Click on “Response Codes” and then on the “Client Errors (4xx)” filter to see unreachable pages. As the tool finds broken links in a 4xx state, in the “Response Codes” tab with the filter “Client Errors (4xx),” you will see the list of results populate. You can wait for the scan to complete until reaching 100%, or you can start thinking about how to fix the error. Alternatively, you can also use the “Overview” window on the right panel and click directly on “Client Errors (4xx)” in the menu under “Response codes.” Regardless of how you get there, the result of the pages will be the same.
  4. Identify the source of broken links from the “Incoming Links” tab.
  5. Click on the “Inlinks” tab located in the bottom panel. In the “From” column, you will find the source of the page containing the broken link in 404, and in the “To” column, there will be the URL of the non-existent page. Scrolling through the columns, you can find other useful information, such as anchor text, any alt text if it’s an image containing the link, attributes, and other useful information.
  6. Export the results to Excel for better visualization or if there is a need to use the results for further checks, you can export both the source and the links found in 404 using the option in the “Bulk Export” menu, “Response Codes,” “Client Errors (4xx).” This way, you will be able to export both the source links and broken links.

How to fix 400 bad request errors

Several reasons could cause a 400 status code. The most common is a syntax error in the URL. Other times, the cause could be an invalid or expired cookie, an attempt to upload a file that is too large, or a browser extension.

But let’s look at them in more detail and especially discover how to fix common 400 bad request errors.

400 bad request error examples

Check the URL syntax

It often happens to include unwanted characters in the URL that is entered in the browser. Remember to always check the spelling, hyphens, and page extension, and make sure you haven’t made typos or entered invalid or disallowed characters.

Also, verify that the path parts in the URL are always separated with a forward slash (/) and never with a backslash (\\\\\\\\).

In some cases, the link clicked on a site may have been entered with a syntax error. If it’s obvious, you could try copying and correcting it in the URL bar and then refreshing the page.

This is the most common cause of a 400 bad request, and it occurs when the web address is incorrect. But if you’re still getting an HTTP 400 status code, it’s time to move on to the next step.

Clear browser cache and cookies

When you browse the Internet and visit different sites, your browser takes small bits of data and temporarily stores them on your computer.

Cookies are nothing more than small pieces of information from a visited site, stored on your computer. By doing this, the next time you visit that same website, the pages will load faster because the stored data in cookies is used.

You might receive 400 bad requests if the cookies stored on your PC are old, outdated, or damaged. How to fix it? you can clear the entire cache or try refreshing the page to get new cookies.

Clearing the browser cache means accepting the new cookies once you revisit that page. There are various ways to clear cookies, and each browser uses a slightly different method.

If you’re using Chrome, here’s a quick and easy trick:

  1. Type “chrome://settings/clearBrowserData” into the navigation bar of Chrome.
  2. Click the “Clear Data” button.
  3. Exit/Close all browser windows and reopen them.

Alternatively, below you can find the official instructions for all the most common browsers:

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Clear DNS cache

Websites use DNS cache to obtain information about online searches. Your computer maintains a temporary database of websites you’ve visited, influencing your search results.

When the DNS data stored on the computer is not synchronized with the information on the Internet, a 400 Bad Request error occurs.

If you encounter a 4xx status code, it might be necessary to clear the DNS cache. After clearing it, the computer will request new DNS information from the nameservers.

The file size is too large

If you receive a 400 bad request message immediately after uploading a file, it may be because the file size is too large and exceeds the server’s file limit, resulting in rejection.

How to resolve it, try uploading different and much smaller files first and see if this solves the issue.

If it works, the initial file is probably too large, and you’ll need to find a way to compress it before attempting to upload it again.

Disable browser extensions

Occasionally, the 400 bad requests could be caused by a browser extension installed on your browser. Try temporarily disabling or uninstalling the most recent installations, restarting the browser, and reloading the page.

To quickly access extensions, type “chrome://extensions/” in the Chrome navigation bar.

Restart system, devices, and router

If you’ve tried all the above fixes and the HTTP 400 error persists, you might want to try the old-fashioned reboot.

Although often ridiculed, the technique of turning off a device and turning it back on is surprisingly effective in resolving various issues.

With the 400 Bad Request error, you could try not only restarting the computer but also any connected devices, especially the router.

Conclusion and practical advice for your site

I hope that with this guide, you’ve been able to better understand what HTTP error 400 means and how to eliminate it permanently.

Remember to periodically check for pages with 4xx status codes, your Search Engine Optimization will benefit, and users will have no reason to leave your site.

If you delete a page, don’t forget to set up redirects to a resource with similar content to avoid losing traffic gained from the old page’s positioning.

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