Varnish and Google Analytics

Question

I don't quite understand how Google Analytics cookies work with Varnish.

• Do pages that contain GA cookie not get cached?
• Do I need to remove the GA cooke in vcl_recv?
• If I do remove them, does that stop GA tracking visitors?

Answer 1

Cookies invalidate the cache if the Vary header is not set. For example, a client that goes to a URL with a certain login cookie will receive a different page than a client with a different cookie.

In order to cache a page that has cookies that do not affect the cache-ability of the page (for example, Google Analytics on static sites), the cookies must be stripped or the cache won't know whether two pages should be considered the same resource.