Today I read the article Perbu on the “cookie monster”. http://www.varnish-software.com/blog/cookie-monster

I do not agree with “If the client sends you a cookie Varnish will not issue a cached page but instead fetch a new page from the backend servers”.

This is more complicated. Varnish does not care if the client (the browser) send a cookie or not. But Varnish take care of the backend response. If the backend sends a response with a cookie, the page can’t be put in the Varnish Cache.

I’m very sure of that, we have a lot of cookie for analytics purpose in our page, they are put by javascript on the client side. For each request of the browser, you can see (using LiveHttpHeader) that cookie are sent to Varnish and yet, Varnish continue to hit in the cache.