html5 meta tag cache-control no longer valid?

Question

How do I define

in HTML5? It is no longer valid according to the W3C Vali

Answer 1

There is no HTML solution. Mozilla's application cache (cache.manifest) is deprecated. The application cache site says:

This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Avoid using it and update existing code if possible. ... Use Service Workers instead.

Apart from that, I suggest you use HTTP Cache-Control to solve cache issues.