Earliest browsers that support if-modified-since or if-none-match headers

Question

Based on my observations, google and probably many others are in love with websites that include the Etag and Last-modified headers along with the if-modified-since and if-none-match header checking because they contribute to higher speed browsing, however, back in the day, headers in use were namely Expires and Cache-control.

I read elsewhere that google chrome browser ignores cache-control sent by the server and uses a value of zero. Because of this, I'm going to stick with using Etag and Last-Modified headers.

My question is what are the first browsers and versions that support Etag, Last-modified, If-modified-since and If-none-match headers?

The reason why I ask is because my site for the most part is a site that displays photos but I don't want people with extremely old computers to throw them out and buy new ones just in order to view a set of pictures. I would rather build a very large set of happy guests instead.

Answer 1

I read elsewhere that google chrome browser ignores cache-control sent by the server and uses a value of zero.

Citation please? The only reference I found of this is a SO question (June 2012) that states that Chrome will override Cache-Control if the user specifically refreshes the page - which is understandable.

This would also be strange since Google recommends Cache-Control headers in its developer guidelines. Cache-Control is the "newer standard" (although still quite old) and should take priority over other headers if present.

what are the first browsers and versions that support Etag, Last-modified, If-modified-since and If-none-match headers?

With regards to ETag / If-None_match, this question on SO (June 2011) states:

all browsers in popular use, IE5.5+, Safari, Chrome, Opera, and Firefox, all support the ETag/If-None-Match headers.

...but it will no doubt predate this list. (ETags were part of the original HTTP/1.1 spec formerly introduced in 1997.)

Last-modified / If-Modified-Since will certainly predate ETags. I would think the very early browsers would have supported these. This represents the basic fundamentals of any caching mechanism.