What's the difference between Cache-Control: max-age=0 and no-cache?

Question

The header Cache-Control: max-age=0 implies that the content is considered stale (and must be re-fetched) immediately, which is in effect the same thing as

Answer 1

One thing that (surprisingly) hasn't been mentioned is that a request can explicitly indicate that it will accept stale data, using the max-stale directive. In that case, if the server responded with max-age=0, the cache would merely consider the response stale, and would be free to use it to satisfy the client's request [which asked for potentially-stale data]. By contrast, if the server sends no-cache that really does trump any request by the client (with max-stale) for stale data, as the cache MUST revalidate.