What's the difference between expires, max-age, and shared max-age?

Question

I have never used HTTP Caching.

I found those caching options on Symfony documentation page.

I just wanted to know what's the difference between expires, max-age, and s-maxage headers?

Answer 1

Shortly: Expires is understand by HTTP/1.0 agents, whereas Cache-control: max-age= was introduced in HTTP/1.1. s-maxage is similar to max-age but it applies to proxies instead of clients.

Answer 2

• Cache-Control:

  Was introduced in HTTP/1.1 and supersedes previous headers (e.g. Expires) used to define response caching policies. All modern browsers support Cache-Control, hence that is all we will need.

• Expires:

  While the Cache-Control header turns on client-side caching and sets the max-age of a resource, the Expires header is used to specify a specific point in time the resource is no longer valid.

• max-age:

  Used on both client and proxy for content expiration

• s-maxage:

  Used only by the proxy for content expiration