HTTP 304 Not Modified indicates which of the following?

• A. Created
• B. Bad Request
• C. Unauthorized
• D. Not Modified - nothing was modified by the request; Returned by Patch, PUT

Answer: (D)

HTTP 304 Not Modified is about how caching and conditional requests work. When a client already has a cached copy of a resource, it can ask the server to revalidate that copy using conditional headers like If-Modified-Since or If-None-Match (with an ETag). If the resource hasn’t changed since the version the client has, the server responds with 304 Not Modified and does not send the resource body. The client then uses its cached copy, saving bandwidth and time.

This status code is not about creating new resources, bad requests, or missing authorization. Those are handled by other codes (like Created for a successful resource creation, Bad Request for invalid input, Unauthorized when authentication is required and missing or invalid). Also, 304 is typically used for GET or HEAD requests that are being validated; PUT or PATCH are usually about updating resources and commonly return 200 or 204 when successful, rather than 304.