This week I’ve decided to better understand X-Magento-Vary cookie. In Magento 2 there might be more than one unique information presented to a user from the same URL.

Purpose

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.

How it works

Any time a user performs an action e.g. Log in, subscribe to a newsletter, add to cart etc. this action changes the state of a system. This state is also known as HTTP context of a system.

The context is identified by various unique parameters which are used to generate unique md5 hash value. Once generated, a hash value is set into an X-Magento-Vary cookie parameter and sent back in an HTTP response.

The X-Magento-Vary cookie is set during HTTP POST or PUT request has been sent to a Magento application.

Varnish server configured as a front-end cache creates a new version of a page based on newly generated X-Magento-Vary cookie.

Context Parameters

In order to generate a hash value, Magento 2 uses parameters which help to differentiate different versions of the same page and with different content on it.

1. “Customer Logged In” parameter is set every to differentiate a page for all guests versus specific information which is only available for logged in customers.
2. “Customer Group” parameter provides information about logged in customer and customer group assigned for a customer. It works when there is catalog price rules or shopping price rules are applied on for a customer group.
3. “Customer Segment” parameter provides similar to customer group information. It allows to additionally split customers into a different segment e.g. age, total order value in order to increase the market, such customers, better. You may find this parameter in Enterprise version only.
4. “Store” parameter is used to show different versions of a page per store.
5. “Current Currency” parameter is used to have different prices on a page according to a currency selected.
6. “Tax Rates” parameter affects prices on pages. Having logged in customer with shipping and billing addresses allows the system to change taxes per customer depending on Tax Rate for a country.

Sometimes for one page stored in Varnish, you may have up to 200 different versions of the same page.