A 400 Bad Request error occurs when the request sent to the site server is incorrect or corrupted and the server receiving the request cannot understand it. Sometimes the problem occurs on the website itself, and you are unlikely to be able to do anything about it. But most of the time the problem is something you can figure out - maybe you typed the address incorrectly, or maybe your browser cache is causing problems. Here are some solutions you can try.

What is a 400 Bad Request error?

The 400 Bad Request error occurs when the server cannot understand the request that has been sent to it. This is called a 400 error because it is the HTTP status code used by the web server to describe such an error.

The 400 Bad Request error can occur due to a simple error in the request. You may have entered the URL incorrectly and for some reason the server is unable to return a 404 error. Or perhaps your web browser is trying to use an expired or invalid cookie. Some servers that are not configured properly may also throw a 400 error instead of more useful errors in some situations. For example, if you try to upload a file that is too large for some sites, you may receive a 400 error instead of an error telling you that maximum size file.

As with 404 and 502 errors, website designers can customize what a 400 error looks like. This way, you may see different 400 error pages on different sites. Websites may also use several different names for this error. For example, you might see things like:

• 400 Bad Request
• 400 Bad Request. The request could not be accepted by the server due to incorrect syntax
• Bad Request - Invalid URL
• Bad Request. Your browser sent a request that this server could not understand
• HTTP Error 400: Invalid request hostname
• Bad Request: error 400
• HTTP Error 400 - Bad Request

Often you can do something to fix a 400 error, but figuring out what exactly can be difficult due to the vague nature of the error. Here are some things you can try.

Refresh the page

Updating the page is always worth it. Many times the 400 error is temporary and a simple update may help. Most browsers use the F5 key to refresh and also provide a Refresh button somewhere in the address bar. This doesn't often fix the problem, but it only takes a second to complete.

Double check the address

The most common cause of a 400 error is an invalid URL. If you entered the URL in address bar yourself, you may have made a mistake. If you clicked a link on another web page and received a 404 error, it is also possible that there was a typo in the link. Check the address for any obvious errors. Also, check for special characters in the URL, especially those you don't often see in URLs.

Perform a search

If the URL you are trying to find is descriptive (or if you know the approximate title of the article or page you are expecting), you can use keywords in the address to search the website. In the example below, you can't really tell from the URL itself if something is wrong, but you can see some of the words from the article title.

Armed with this knowledge, you can search the website for relevant keywords. This should take you to the correct page.

This same solution also works if the website you are trying to reach has changed the URL for some reason and has not redirected the old address to the new one.

And if a website doesn't have its own search box, you can always use Google (or any other search engine, which you prefer). Simply use the "site:" operator to search only the matching site for the keywords.

In the image below we are using Google and search phrase"site:site the local network» to search only the site site by keywords.

Clear your browser cookies and cache

Many websites (including Google and YouTube) report a 400 error because the cookies they read are either corrupted or too old. Some browser extensions can also modify your cookies and cause a 400 error. It is also possible that your browser has cached a corrupted version of the page you are trying to open.

To test this feature, you need to clear your browser cache and cookies. Clearing the cache won't affect your browsing experience much, but some websites may take a few extra seconds to load as they re-download all previously cached data. Cleaning cookies means you will have to log in again to most websites.

Clear your DNS

Your computer may be storing outdated DNS records that are causing errors. Simply clearing your DNS records may help resolve the issue. It's easy to do and won't cause any problems.

Check the file size

If you upload a file to a website and you get a 400 error, then there is a chance that the file is too large. Try uploading the file smaller size to confirm if this caused the problem.

Try other sites

If you try to open one website and get a 400 error, try opening other websites to see if the problem persists. If so, it may be a problem with your computer or network equipment, not the website you are trying to open.

Restart your computer and other hardware

This solution is a hit and rebooting your computer and especially your network equipment (routers, modems) is a common way to get rid of many server errors.

Contact website

If you have tried all the solutions and the error does not disappear, it means that the site itself may have problems. Try contacting the website on the contact page (if that works) or via social media. Chances are they are already aware of the problem and are working to fix it.

If you receive that message when installing a program, it means the installer you are using is a web installer. When you are using this kind of installer, the entire installation process requires internet connection that’s why you cannot disconnect from the internet while the program is being installed. If you don’t want to see this error, you should download the standalone installer.

A standalone or offline installer does not require internet connection because the file itself is the complete setup or installer package. To troubleshoot your problem, check your connection. If your computer is connected to a Wi-Fi router, try resetting the router. If the router has a power button, press it to turn it off then unplug the router from the power for about 10 to 20 seconds.

Press any button on the router to drain any leftover power. After this, plug the router back to the power and turn it on. When the router is ready, try installing the program again and see if it works.

Error 400 (Bad Request) is an HTTP response code , which means that the server was unable to process the request sent by the client due to invalid syntax. These HTTP response codes reflect the complex relationships between the client, the web application, the server, and often several third-party web services at once. This can make it difficult to find the cause of an error, even within a controlled development environment.

In this article we will look at what the 400 Bad Request error means (translated as “Invalid request”) and how to fix it

Server side or client side?

All HTTP response codes in the 4xx category are considered client-side errors. Despite this, the appearance of a 4xx error does not necessarily mean that the problem has anything to do with the client, which refers to the web browser or device used to access the application. Often, if you are trying to diagnose a problem with your application, you can immediately ignore most of the client code and components such as HTML, Cascading Style Sheets ( CSS), client-side JavaScript code, etc. This also applies to more than just websites. Many smartphone applications that have modern user interface, are web applications.

On the other hand, a 400 Bad Request error means that the request sent by the client was incorrect for one reason or another. The user client may try to download too big file, the request may be malformed, the HTTP request headers may be incorrect, and so on.

We'll look at some of these scenarios ( and potential solutions) below. But keep in mind: we cannot definitively rule out either the client or the server as the source of the problem. In these cases the server is network object, generating a 400 Bad Request error and returning it as an HTTP response code to the client, but perhaps the client is responsible for the problem.

Start with a thorough application backup

It is important to make a complete backup of your application, database, etc. before making any edits or changes to the system. Even better, it is possible to create a full copy of the application on an additional intermediate server that is not publicly accessible.

This approach will provide a clean testbed in which you can try out all possible scenarios and potential changes to fix an issue without compromising the security or integrity of your live application.

Diagnosis of error 400 Bad Request

Error 400 Bad Request means that the server ( remote computer ) cannot process a request sent by the client (browser) due to a problem that the server interprets as a client-side problem.

There are many scenarios in which a 400 Bad Request error can appear in an application. Below are some of the most likely cases:

• The client accidentally (or intentionally) sends information that is intercepted by the false request router. Some web applications look for special HTTP headers to process requests and ensure that the client is not doing anything malicious. If the expected HTTP header is not found or is incorrect, then a 400 Bad Request error is a possible result.
• The client may be uploading a file that is too large. Most servers or applications have a limit on the size of the downloaded file. This prevents clogging of the channel and other server resources. In many cases, the server will issue a 400 Bad Request error when the file is too large and therefore the request cannot be completed.
• The client is requesting an invalid URL. If a client sends a request to an invalid URL ( incorrectly composed), this may result in a 400 Bad Request error.
• The client is using invalid or outdated cookies. This is possible because the local cookie in the browser is a session identifier. If a particular session token matches a request token from another client, then the server/application may interpret this as a malicious act and issue a 400 Bad Request error code.

Fixing client side issues

Error 400 Bad Request ( try later) it's better to start with a fix on the client side. Here are some tips to try on the browser or device that's giving you the error.

Check the requested URL

The most common cause of the 400 Bad Request error is simply entering an incorrect URL. Domain names (for example, website) are case-insensitive, so a mixed-case reference like this works the same as the normal lowercase version. But the parts of the URL that come after the domain name are case sensitive. Unless the application/server specifically pre-processes all URLs and converts them to lowercase before executing the request.

It is important to check the URL for inappropriate special characters that should not be there. If the server receives an invalid URL, it will respond with a 400 Bad Request error.

Clear relevant cookies

One potential cause of a 400 Bad Request error is invalid or duplicate local cookies. HTTP cookies are small pieces of data stored on the local device that are used by sites and web applications to “remember” a specific browser or device. Most modern web applications use cookies to store browser- or user-specific data, identifying the customer and making future visits faster and easier.

But cookies that store session information about your account or device may conflict with another session token from another user, giving one (or both of you) a 400 Bad Request error.

In most cases, it is sufficient to only consider your application for the cookies that are specific to the site or web application that is throwing the 400 Bad Request error.

Cookies are stored based on the domain name of the web application, so you can delete only those cookies that match the site's domain, leaving other cookies intact. But if you are not familiar with manually deleting specific cookies, it is much easier and safer to clear all cookies at once.

It can be done different ways depending on the browser you are using:

• Google Chrome;
• Internet Explorer;
• Microsoft Edge;
• Mozilla Firefox;
• Safari.

Upload a smaller file

If you receive a 400 Bad Request error when downloading a file, try it out on a smaller file. This includes "downloads" of files that won't load from your local computer. Even files sent from other computers count as "uploads" from the perspective of the web server running your application.

Sign out and sign in

Try logging out and logging back in. If you have recently cleared your browser cookies, this will automatically log you out the next time you load the page. Just try logging back in to see if the system works correctly.

Also, the application may encounter a problem related to your previous session, which is just a string that the server sends to the client to identify the client for future requests. As with other data, the session token ( or session string) is stored locally on your device in cookies and is transmitted by the client to the server with each request. If the server decides that the session token is invalid or compromised, you may receive a 400 Bad Request error.

In most web applications, logging out and logging back in causes the local session token to be regenerated.

Debugging on common platforms

If you are using common software packages on your server that generate a 400 Bad Request error, examine the stability and functionality of these platforms. The most common content management systems such as WordPress, Joomla! and Drupal, are well tested in their basic versions. But once you start changing the ones they use PHP extensions, it is very easy to provoke unexpected problems that will result in a 400 Bad Request error.

Rollback recent changes

If you updated your content management system just before the 400 Bad Request error appeared, consider rolling back to the previous version that was installed as the fastest and easiest way remove the 400 bad request error.

Likewise, any extensions or modules that have been updated may cause errors on the server side, so rolling back to previous versions of those extensions may also help.

But in some cases, CMSs do not provide the ability to roll back to previous versions. This usually happens with popular platforms, so don't be afraid if you can't find an easy way to get back to using old version one or another software platform.

Remove new extensions, modules or plugins

Depending on the specific CMS that the application uses, the names of these components will vary. But in all systems they serve the same purpose: improving the capabilities of the platform relative to its standard functionality.

However, keep in mind that extensions can somehow gain full control over the system, making changes to the PHP, HTML, CSS, JavaScript or database code. Therefore, a wise decision may be to remove any new extensions that have been recently added.

Check for unintentional changes to the database

Even if you deleted an extension through the CMS control panel, this does not guarantee that the changes it made were completely undone. This applies to many WordPress extensions that are given full access to the database.

An extension can change records in the database that do not "belong" to it, but are created and managed by other extensions ( or even the CMS itself). IN similar cases The module may not know how to roll back changes made to database entries.

I have personally encountered such cases several times. Therefore, the best way is to open the database and manually view the tables and records that may have been modified by the extension.

Finding problems on the server side

If you are sure that the 400 Bad Request error is not related to the CMS, here are some additional tips that may help you find the problem on the server side.

Have you recently downloaded software packages from the Internet? This is the most commonly used infiltration technique right now. Many PC users prefer to install software packages, which saves time and effort. The problem is that you have to pay close attention to the process. Select the Advanced/Custom option in the installation wizard. Remember that skipping installation steps decisive mistake. There could be a whole bunch of viruses attached safe programs in the package. If you are careless, you will install infections as well. It is much easier to prevent infiltration than to remove a virus. Save yourself and be careful. Also, check the EULA ( license agreement end user) from what you download. The same piece of advice goes for terms and conditions. Take your time in the installation and don't lose sight of possible threats. Also, stay away from illegal websites, torrents and advertisements. Most often those are unreliable.

Why are these ads dangerous?

Warning, multiple virus scanners have detected possible malware in Error.

Antivirus software	Version	Detection
McAfee	5.600.0.1067
Kingsoft AntiVirus	2013.4.9.267	Win32.Troj.Generic.a.(kcloud)
Tencent	1.0.0.1	Win32.Trojan.Bprotector.Wlfh
Qihoo-360	1.0.0.1015	Win32/Virus.RiskTool.825
ESET-NOD32	8894	Win32/Wajam.A
NANO AntiVirus	0.26.0.55366	Trojan.Win32.Searcher.bpjlwd
VIPRE Antivirus	22702	Wajam (fs)
Baidu-International	3.5.1.41473	Trojan.Win32.Agent.peo
Dr.Web		Adware.Searcher.2467
Malwarebytes	1.75.0.1	PUP.Optional.Wajam.A
McAfee-GW-Edition	2013	Win32.Application.OptimizerPro.E

Error behavior

• Distributes via pay-to-install or bundled with software third party manufacturers.
• Installs itself without permissions
• Shows fake security alerts, pop-ups and advertisements.
• Error deactivates installed software.
• Error shows commercial advertisement
• Changes user Home page
• Browser redirection to infected pages.
• Steals or uses your confidential data
• Change desktop and browser settings.

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Error carried by Windows OS versions

• Windows 10 20%
• Windows 8 37%
• Windows 7 19%
• Windows Vista 8%
• Windows XP 16%

Geography Error

Eliminate Error from Windows

Remove from Windows XP Error:

Remove Error from your Windows 7 and Vista:

Erase Error from Windows 8 and 8.1:

Remove Error from your browsers

Error Removal from Internet Explorer

Erase Error from Mozilla Firefox

Stop Error from Chrome

Who among those who like to surf the Internet has not encountered the “400: Bad request” error appearing in the browser? True, not all surfers know what it means and why it occurs. Now we will try to clarify this situation.

400 Bad request: what does this error mean?

As is believed in the computer world, error number 400 is purely user-related when entering an incorrect request (URL) to access a specific site on the World Wide Web. We beg to differ.

Of course you can enter incorrect address, but sometimes even with the correct address or link being opened, the “HTTP: 400 Bad request” error appears again and again. There can be many reasons for this. This is especially often evident when accessing personal hosting services hosted on different, independent servers from different providers. What is the reason?

Request syntax errors

Indeed, one of the root causes can be called a violation of the correct entry of the page address. Let’s take a simple example: when trying to access the same mail server Mail.ru, a Ukrainian user can enter a URL in the address bar that seems to correspond to his region (in this case, let’s say it is the mail.ua address).

In reality, such a site with a postal service does not exist in nature. It is clear that any Internet browser will immediately display the message “400: Bad request”. But even with this formulation of the question, you can find a bunch of other reasons for the access error.

"400: Bad request Nginx" error problem

The Nginx system itself is either a specific mail server proxy or web server running under UNIX systems.

Typically, errors of this kind are associated with an incorrect server response for a request from a specific IP address. The error results are recorded in a special LOG file, after which they are automatically entered into the firewall as unreliable. Thus, hosting operations are disrupted, regardless of what operating system or browser is used in this situation.

Firewall Impact

As is already clear, the “400: Bad request” error often occurs when a firewall blocks a request.

A way out of this situation may be to add the site address or access device to the list of exceptions. For Windows systems, this is done by accessing the security menu located in the standard “Control Panel”.

In principle, there is nothing wrong even with disabling the firewall completely (of course, if you have a powerful antivirus package). Some clarifications also need to be given on this score.

Antivirus exclusion list

As a rule, the most common standard antivirus packages have their own built-in firewall. It can also block potentially unsafe or unwanted content.