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Client errors (4xx)

400 Bad Request

The server could not understand the request.

Quick answer

A 400 means the server thinks the request was broken, too big or badly formed. Often a damaged cookie or a mistyped address causes it.

When to wait: Waiting rarely helps; try the steps first.

If you are visiting the website

  1. Clear this site's cookies only Delete the cookies and saved data for this one website, not for all websites. Your other logins stay intact.
  2. Check the address Look for typos in the web address, such as a missing letter or the wrong ending (.com instead of .de).
  3. Try a private window Open the site in a private (incognito) window. If it works there, an extension or saved site data may be the cause.

If you run the website

  1. Check server error logs Look at your web server and application logs for the time of the error. They usually name the exact cause.
  2. Check header and cookie sizes Large cookies can push requests over server limits. Reduce what you store in cookies.

Likely causes

  • Common A damaged or very large cookie for this site. (Your side)
  • Sometimes A broken or overly long link. (Your side)
  • Sometimes A bug in the website or its forms. (Website side)

Is the website down? Check it now

One measurement point. Results explain what we saw, not a worldwide verdict.

Sources

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