cache-control headers with last-modified in the past-CodePudding

I get the following header on CURL request.

Am I correct to assume that because the last-modified is that back in the past - the request is not cached in the browser?

➜ curl -I https://dommain.com/assets/sounds/intro.mp3                                                                                               
HTTP/2 200 
date: Sat, 12 Nov 2022 23:39:39 GMT
content-type: audio/mpeg
content-length: 33976
last-modified: Tue, 01 Jan 1980 00:00:01 GMT
etag: "12cea601-84b8"
cache-control: no-cache
accept-ranges: bytes
strict-transport-security: max-age=15724800; includeSubDomains

CodePudding user response：

No. You might be thinking of the Expires header. In the absence of Cache-Control an Expires header with a date in the past would mean that the cached response couldn't be used without revalidation.

In this case, the cache policy is set by the Cache-Control: no-cache header. That means that the browser can store the response, but can't serve it without confirming that it's up to date by making a conditional request.

Since the response has an ETag header, that will be used to determine if the cached response is still valid or not. In the absence of ETag, Last-Modified would be used for that purpose.

In sum, what you have here is a perfectly standard approach to caching, especially for large files. The response can be stored indefinitely, but can only be served from the cache after the origin server has confirmed that the stored response is still valid.