Will proxies cache HTTP Responses when authentication is provided?

Question

Given a URI which has headers for caching properly configured.

If two users make a request to the same URI but provide two different sets of credentials, will a proxy cache the response per user+URI, or per URI, or not at all?

Answer 1

The response will only be used for other users if the Cache-Control response header contains the public directive. Apart from that, the proxy must not cache a response to an authorized request.

Read the section Authorization of the HTTP 1.1 standard for all the details.