400
Universal HTTP Status Code
Severity: ModerateWhat Does This Error Mean?
A 400 Bad Request error means the website's server received your request but could not understand it. Something about the request was malformed or incorrect. The server is refusing to process it — not because of a password issue, but because the request itself is broken. This usually happens on the browser or app side, not the website's servers.
Affected Models
- All web browsers
- All websites and web apps
- Mobile browsers
- API clients
Common Causes
- A corrupted or outdated browser cookie is confusing the server
- The URL contains invalid characters or is formatted incorrectly
- Your browser cache has stored old, broken data about the site
- A form you submitted contained data the server cannot read
- A browser extension is interfering with how the request is sent
How to Fix It
-
Reload the page. Press Ctrl+F5 on Windows or Cmd+Shift+R on Mac to force a fresh load.
Sometimes a one-time glitch causes a bad request. A hard refresh often clears it.
-
Clear your browser's cookies and cache. In Chrome: go to Settings > Privacy > Clear browsing data. Check both 'Cookies' and 'Cached images and files', then click Clear.
Old cookies are one of the most common causes of 400 errors.
-
Check the URL in your address bar. Look for any strange characters, double slashes, or spaces. If you typed the address manually, try retyping it carefully.
A single misplaced character in a URL can cause this error.
-
Try opening the page in a private or incognito window. This uses no saved cookies or cache.
If the page loads fine in private mode, the problem is in your stored browser data.
-
Disable your browser extensions one by one, then reload the page. Some ad-blockers and privacy tools interfere with requests.
Re-enable extensions one at a time to find the culprit.
When to Call a Professional
If you are a website visitor seeing this error, there is little you can do beyond the steps below. If the error appears on every site or persists after clearing your cache and cookies, contact your internet service provider. If you own the website, consult a web developer — the server may need configuration changes.
Frequently Asked Questions
Is the 400 error my fault or the website's fault?
Usually it starts on your side — a bad cookie, old cache, or broken URL. But sometimes the website itself sends requests incorrectly. Try the fix steps first. If every visitor sees the error, it is the website's problem.
Will clearing my cookies log me out of websites?
Yes — clearing cookies will sign you out of most websites. You will need to log back in after. It is a small inconvenience but often fixes the 400 error immediately.
Can a 400 error cause any harm to my computer?
No — a 400 error is just a communication problem between your browser and the website. It cannot damage your computer or compromise your data. It just means the page did not load.