浏览器是否支持 s-maxage？

Question

I have a hard time finding out if s-maxage is supported by browsers, or by which versions of them.

s-maxage is primarily meant for shared caches, eg proxies or CDNs, but it seems to me that it also works in Chrome. For example, with a Next.js app that uses the recommended cache-control header like this:

cache-control: public, s-maxage=10, stale-while-revalidate=59

I'm seeing this behavior in Chrome:

However, I can't find a definitive resource like a MDN document or anything that would document it. Anyone knows?

Answer 1

You should not expect browsers to respect s-maxage .

As defined in the specification , s-maxage only applies to shared caches. A browser cache is generally considered to be a private cache.

I think what you're seeing is just the default caching that browsers do if you're not explicit about expiration. Since none of your headers provide an explicit freshness lifetime , the cache is free to assign its own heuristic freshness . It's normal to see a cache hit even if you don't provide any expiration directives.

It is possible that the browser takes s-maxage into account when computing its heuristic freshness, but I certainly wouldn't rely on it.