Responses
Client errors
Distinguish bad input, missing authentication, forbidden access, missing resources, conflicts, and rate limits using common 4xx responses.
8 minute lesson
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Use a 4xx response when the server cannot fulfill the request as sent.
400 Bad Request: invalid syntax or input.401 Unauthorized: authentication is missing or invalid.403 Forbidden: the user is known but not allowed.404 Not Found: the target resource does not exist.409 Conflict: the request conflicts with current state.422 Unprocessable Content: the body is understood but fails semantic validation.429 Too Many Requests: the client exceeded a rate limit.
A useful error response explains what the client can fix. An API might return JSON with an error code and field-level details, while an HTML site may render a helpful page.
Do not leak secrets, stack traces, or database details in a public error body.
Lesson completed