HTTP status codes for web diagnostics

Successful responses

A 200 can still contain an error message, login screen, empty template, noindex directive, or unintended canonical. Inspect the representation.

• 200 OK: the request succeeded; the meaning of the content depends on the method.
• 204 No Content: the request succeeded and the response has no content.
• 206 Partial Content: the server is fulfilling a valid range request with selected content.

Redirect responses

Record the Location field and follow the entire bounded chain. Status alone does not show whether the destination is equivalent or healthy.

• 301 Moved Permanently and 308 Permanent Redirect state a permanent move.
• 302 Found and 307 Temporary Redirect state a temporary move.
• 303 See Other points the client to another resource, commonly after a non-GET request.
• 304 Not Modified is a cache-validation response, not a normal redirect to another URL.

Client-error responses

• 400 Bad Request: the server cannot or will not process the request because of a client-side error.
• 401 Unauthorized: authentication credentials are required or insufficient for the request.
• 403 Forbidden: the server understood the request but refuses to fulfil it.
• 404 Not Found: the server did not find a current representation or is not willing to disclose one.
• 410 Gone: the resource is no longer available and the condition is likely permanent.
• 429 Too Many Requests: the client sent too many requests in a given time.

Server-error responses

Group repeated 5xx responses by route, upstream, time, and deployment. One row establishes an observed failure, not its root cause.

• 500 Internal Server Error: the server encountered an unexpected condition.
• 502 Bad Gateway: a gateway or proxy received an invalid upstream response.
• 503 Service Unavailable: the server is temporarily unable to handle the request.
• 504 Gateway Timeout: a gateway or proxy did not receive a timely upstream response.