: Why doesn't FireFox cache my JavaScript file? I've been trying to figure out why Firefox does not cache my JavaScript file. I don't have this issue with Chrome or IE. Here is what my server's

@Kristi941

It is not recommended to cache resources with a query string. A query string usually represents a dynamic resource. However IE and Chrome do cache based off the Cache-Control and Expires headers. Firefox should cache, however, this could be due to a weak validation i.e. no usage of Etag. Using Etag forces strong validation of the cache-control mechanism for Firefox. Firefox tries to follow the RFC 2616 section 13.3.2. If the file has not changed on the server you should see a response of 304 Not Modified.


13.9 Side Effects of GET and HEAD

Unless the origin server explicitly prohibits the caching of their
responses, the application of GET and HEAD methods to any resources
SHOULD NOT have side effects that would lead to erroneous behavior if
these responses are taken from a cache. They MAY still have side
effects, but a cache is not required to consider such side effects in
its caching decisions. Caches are always expected to observe an
origin server's explicit restrictions on caching.

We note one exception to this rule: since some applications have
traditionally used GETs and HEADs with query URLs (those containing a
"?" in the rel_path part) to perform operations with significant side
effects, caches MUST NOT treat responses to such URIs as fresh unless
the server provides an explicit expiration time. This specifically
means that responses from HTTP/1.0 servers for such URIs SHOULD NOT
be taken from a cache. See section 9.1.1 for related information.


So you should assume that query string should not cache dynamic content which includes html. This however is not the case for IE and Chrome which pay attention to the Cache-Control and Expires headers for as given requested URI.

With that said it really depends on the implementation of the client and server.

In firefox when reloading using F5 key and examining the Developer Tools you should see 403 Not Modified for Cache Hits when using e-tag header.

So try to enable ETag support within IIS.

References: www.mobify.com/blog/beginners-guide-to-http-cache-headers/

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