X-Magento-Vary cookie is used by Magento 2 system to highlight that version of a page requested by a user has been changed. It allows having different versions of the same page stored in cache e.g. Varnish.
X-Magento-Vary cookie is used by Magento 2 system to highlight that version of a page requested by a user has been changed. It allows having different versions of the same page stored in cache e.g. Varnish.