How to Fix a 400 Bad Request Error on Your WordPress Site
If you’re reading this article, you’re probably getting tired of the 400 Bad Request message when you try to access a website. You’ve reloaded the page, used a different device, and tried various browsers, but nothing seems to work. So, what does 400 Bad Request mean? How can you solve this error? Let’s find out.
What does a 400 Bad Request error mean?
A 400 Bad Request error is part of the HTTP 4XX status codes, which indicate the server can’t fulfill requests because of a client-side error. It usually occurs when your request is corrupted, invalid, or too big. As a result, the server can’t process the request and shows a 400 response code instead.
How to fix a 400 Bad Request error
Check your internet connection
When you attempt to access a website, your browser sends a request to the server, which then sends back a response. A slow internet connection can cause the data to be transmitted incompletely, leading to the 400 status code. So, before trying other troubleshooting methods, it’s a good idea to test your internet speed using a tool like Google Fiber. For web browsing, a good ping rate should be between 51 to 150 milliseconds (ms). Anything beyond that means your internet connection is slow. In that case, try using another network and see if the 400 error is solved. If your connection works just fine, but the error remains, move on to the second step.
Fix typos and invalid characters in the URL
Every time you enter a URL in the address bar, make sure there are no spelling mistakes or incorrect use of special characters. If you suspect that the URL is incorrectly encoded, use an encoder/decoder tool to decode the URL back to its original format. After that, re-encode the URL following the proper syntax and format.
Clear your browser’s cache and cookies
Cache is a temporary storage location used to keep copies of all web pages you have ever visited. Meanwhile, cookies save your personal information like browsing history, login details, and preferred settings. For instance, you can easily open password-protected pages without having to enter your credentials each time. But there’s always two sides of the same coin. As helpful as they are, cache and cookies can become corrupted or outdated. To avoid it, the easiest way is to clear browsing data on a regular basis. If you’re a Google Chrome user, follow these steps:
- Click the three dots at the top right corner of Google Chrome and select Settings.
- Find the Privacy and security section and choose Delete browsing data.
- Select Cached images and files and Cookies and other site data.
- Set your preferred time range – we recommend all time.
- Click Clear data, and that’s it.
Deactivate browser extensions
Some browser extensions interact directly with cookies. Think about password managers that store your login credentials, or ad blockers that keep a list of blocked domains and known ad scripts. Many browser add-ons may also modify HTTP headers, block JavaScript scripts, and conflict with other extensions – all of which can trigger a 400 error. Try disabling all your extensions temporarily to see if the error disappears. After that, refresh the web page that was displaying the 400 error. If the page loads correctly, this means one of the extensions was causing the problem. Re-enable the extensions one by one, while refreshing the page after each activation. If the 400 error re-occurs, the most recently enabled extension is likely responsible. Try updating the suspect extension to see if this resolves the issue. If the extension is up-to-date, you may need to remove it and find a substitute.
Flush the DNS cache
Domain name system (DNS) stores the domain name and IP address of every website. By default, these DNS records are stored in your computer’s local cache to speed up loading on repeat visits. However, sometimes a website may change its IP address. When that happens, the cached data becomes outdated, resulting in the HTTP 400 error. This is why you need to clear the local DNS cache regularly, so your system can retrieve the most up-to-date DNS information. Here’s how to flush DNS cache on different operating systems:
- Windows: Type in cmd in the Windows Search and press Enter. Enter ipconfig /flushdns in the command prompt window and press Enter.
- macOS: Use the Spotlight search to find and access the Terminal app. Once opened, enter the following command and press Enter: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
Besides your operating system, you have to remove the outdated DNS cache in your web browser. For Google Chrome users, simply type chrome://net-internals/#dns in the address bar and press Enter. Then, click Clear host cache to flush the DNS cache within Chrome.
Compress your files
Web servers usually set an upload limit to preserve storage space and prevent timeouts. So if you upload a file that’s larger than the allowed size, the server won’t be able to handle your request. In that case, reduce your file size before trying to upload it again. There are tons of free online tools you can use, like HiPDF for PDF files, TinyPNG for images, and Media.io for videos and audio files. Keep in mind that compressing a file may affect its quality. Always double-check your multimedia content to make sure it isn’t blurry after the compression.
How to audit your website for 4XX error codes
We’ve talked about solving a 400 Bad Request error for users. But what about website owners? How can you ensure that your site is free from 4XX errors? The answer is a regular website audit. Every once in a while, open your website from different browsers to see if any 4XX response code pops up. You can also use a tool like Ahrefs to perform a thorough site audit:
- Open Ahrefs and navigate to Site Audit.
- Click + New Project, then import your website from Google Search Console or add it manually.
- Once added, trigger a new crawl and let Ahrefs analyze your site.
- After the report is finished, go to All issues from the left menu.
- Below Internal pages, you will see a list of 4XX errors within your site. From there, click the question mark (?) button to learn more about the error details, such as which URLs are affected and the necessary steps to fix it.
Conclusion
A 400 Bad Request error happens when something is wrong with your request. It’s either because you enter an invalid URL, your cache files and cookies are outdated, or you upload a file that exceeds the server’s limits. Luckily, fixing this error doesn’t require any technical knowledge. Use a fast network connection, make sure the URL is correct, clear browser cache and cookies, turn off browser extensions, flush the DNS cache on your computer, and reduce the files you want to upload. If you’re a website owner, you also need to perform a regular audit to keep your site free from any 4XX errors.
400 Bad Request FAQ
Is a 400 Bad Request error a client-side or server-side issue?
Just like any other 4XX status code, a 400 Bad Request response often occurs due to a client error, such as incorrect URL syntax, invalid request headers, or oversized file uploads.
How to fix 400 Bad Request on Google Chrome?
The easiest way to resolve a 400 Bad Request error on Chrome is to clear your browser cache and cookies. Simply open the three-dot icon, choose Delete Browsing Data, set the time range, and click Clear data. You can also disable your browser extensions one by one to find which one is causing the error.
Are there any tools that can help me debug a 400 Bad Request error?
You can use browser developer tools like Chrome DevTools to debug 400 Bad Request errors and other HTTP issues. They allow inspection of HTTP requests and responses to identify issues with request formatting, rates, and methods. If you run a WordPress website, follow our guide to enable the WordPress debug mode.
Ariffud Muhammad
Ariffud is a Technical Content Writer with an educational background in Informatics. He has extensive expertise in Linux and VPS, authoring over 200 articles on server management and web development. Follow him on LinkedIn.
Brian Fajar Mauladhika
Brian is a Content Writer who loves telling complex stories in a simple way. He has written all types of content, including tutorials, blog posts, landing pages, social media posts, white papers, infographics, and YouTube scripts. Follow him on LinkedIn.
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