I send back an image with the following HTTP response header:
Cache-Control: private,max-age=86400
My understanding is that the browser should not even ask for this file for 24 hours (86,400 = 60s * 60m * 24h).
What I'm seeing on subsequent requests is that it still asks for the file, but gets back a "304 Not Modified." This is good, but I want to remove even that request/response.
What header is required to prevent the browser from even bothering to ask for the file, and just have it blindly use the file it has in local cache, until that file expires?