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From a browser perspective,
What occur if a component (image, script, stylesheet...) is served without a Last-Modified HTTP header field...
Is it however cached by the browser even if it won't be able to perform a validity check(If-Modified-Since) in future, due to his lack of date/time information?
Eg:
GET /foo.png HTTP/1.1
Host: example.org
--
200 OK
Content-Type: image/png
...
Is foo.png however cached?
--
Would you know any online service to serve my raw HTTP response that I can write myself in order to test what I'm asking ?
Thank you.
482
Cache-Control is a HTTP cache header that contains a set of parameters to define the browser's caching policies in the client requests and server responses. When a client makes a request to the server, the browser can cache, or store copies of resources for faster access and lower latency.
Without the cache control header the browser requests the resource every time it loads a new(?) page.
The If-Modified-Since HTTP header indicates the time for which a browser first downloaded a resource from the server. This helps determine whether or not the resource has changed since the last time it was accessed.
To use cache-control in HTML, you use the meta tag, e.g. The value in the content field is defined as one of the four values below. HTTP 1.1. Allowed values = PUBLIC | PRIVATE | NO-CACHE | NO-STORE.
Generally speaking, responses can be cached unless they explicitly say that they can't (e.g., with cache-control: no-store).
However, most caches will not store responses that don't have something that they can base freshness on, e.g., Cache-Control, Expires, or Last-Modified.
For the complete rules, see: https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-p6-cache-13#section-2.1
See: http://www.mnot.net/blog/2009/02/24/unintended_caching for an example of how this can surprise some people.
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