400 Bad Request

What it means

Common causes are invalid JSON, a malformed URL, missing required fields, or headers that are too large or corrupted.

Common causes

• Invalid JSON or form data in the request body.
• A corrupted or oversized cookie.
• Invalid characters in the URL.

How to fix it

1. Validate the request body and query parameters.
2. Clear the site's cookies and try again.
3. Check the API documentation for required fields.

Example response

HTTP/1.1 400 Bad Request
Content-Type: text/plain; charset=utf-8

Worked example

A client sends a request the server cannot fulfill as submitted. Check the response body and request details, correct the input or permissions, and retry only after the relevant issue is resolved.

How to read this response

1. Find the status line in your browser's Network panel, API client, or server access log.
2. Read the response body and headers shown above; headers such as Location, Allow, Retry-After, and WWW-Authenticate explain the next step.
3. Use the code's class to orient your diagnosis: informational, successful, redirected, request-related, or server-side.

How to check a status code

Enter a URL in the HTTP Status Checker to see its status code, every redirect hop, and response time. For redirect-heavy pages, the Website Speed Test shows how much time redirects add.

Frequently asked questions

What it means: HTTP 400

400 Bad Request: The server cannot process the request because it is malformed.

Common causes: 400

Invalid JSON or form data in the request body. A corrupted or oversized cookie. Invalid characters in the URL.

How to fix it: HTTP 400

Validate the request body and query parameters. Clear the site's cookies and try again. Check the API documentation for required fields.

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