Question

I would like to set a far future date for Expires for some commonly used but relatively unchanging content but am wondering how to inform web / browser cache to get the latest content from the server in case I have to unexpectedly push new stuff to the user?

Answer 1

Add a query string with e.g. a version number or a timestamp.

<link rel="stylesheet" href="style.css?v=1.1" />
<script src="script.js?v=1.1"></script>
<img src="image.png?v=1.1" />

The webbrowser considers an URL with a different query string as an entirely distinct resource and will therefore be forced to fire a new HTTP request on it if not requested before instead of obtaining the one with the same URI from the cache.

Changing the file name can also, but is plain clumsy.