lightmy.dayINSTANT ANSWERS

Client error

HTTP 400: Bad Request

HTTP 400 means the server could not understand the request.

Meaning

The request is malformed or invalid before application-specific processing can continue.

Common causes

Bad JSON, invalid query parameters, malformed headers, or wrong request encoding can cause it.

What to check

Validate the request body, query string, headers, and Content-Type.

Example response

HTTP/1.1 400 Bad Request

References

Registry: IANA HTTP Status Code Registry
Spec: RFC 9110 §15.5.1
Guide: MDN 400 Bad Request

Related HTTP status codes

Nearby codes often answer the next debugging question.

401 UnauthorizedHTTP 401 means authentication is required or failed.403 ForbiddenHTTP 403 means the server understood the request but refuses access.404 Not FoundHTTP 404 means the server could not find the requested resource.