Static caching can only be used if the visitor's context is known. The context contains a great deal of information that cannot be deduced from the URL alone: currency, user groups, choice of cookies, taxes to be applied, etc. This context is stored in a cookie called "jpresta_cache_context".
This context is stored in a cookie named "jpresta_cache_context", which is added when the user displays a 1st page. Once the cookie is present, the static cache can be used.