Question

When using Cache-Control and Expires header so that a page won’t expire in 10 years:

Cache-Control: max-age=315360000
Expires: Sun, 19 Jul 2020 18:06:32 GMT

will using line 1 have identical result as line 2?

<link href="/public/doc.css?v=128" ... >

<link href="/public/doc_v128.css" ... >

I was thinking maybe some browser will take the ?v=128 as a somewhat more dynamic content and reload it before the 10 year expiration?

Otherwise, both files will expire in 10 years and when there is changes to the CSS, the 128 can be updated to 129 and it will be loaded for sure and have a brand new 10 year expiration date?

(the same goes for javascript .js files)

Answer 1

Using a changing value in the querystring may work against you. According to Google’s Page Speed Optimize caching Performance Best Practice:

Don’t include a query string in the URL for static resources

Most proxies, most notably Squid up
through version 3.0, do not cache
resources with a “?” in their URL even
if a Cache-control: public header is
present in the response. To enable
proxy caching for these resources,
remove query strings from references
to static resources, and instead
encode the parameters into the file
names themselves.

Also, you may want to reconsider 10 years. According to the Header Field Definitions > Expires section of RFC 2616, one year is the max.

To mark a response as “never expires,”
an origin server sends an Expires date
approximately one year from the time
the response is sent. HTTP/1.1 servers
SHOULD NOT send Expires dates more
than one year in the future.