400 Bad Request

What 400 Bad Request means {#what}

Something about the request is malformed — bad syntax, invalid parameters, missing required fields, or mangled JSON. The server won’t process it and won’t try to guess what you meant. The problem is on the client side.

When you’ll see a 400 {#when}

• Sending invalid JSON in a request body
• Missing required query parameters
• Malformed headers
• Sending the wrong data type for a field

When to use 400 {#use}

• Use as a catch-all for malformed requests, but prefer more specific codes when available (422 for validation errors, 415 for wrong content type)
• Always include a helpful error message in the body explaining what’s wrong