X-Magento-Vary aka HTTP Context

X-Magento-Vary aka HTTP Context

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 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 to have different versions of a 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 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, hash value is set into a X-Magento-Vary cookie parameter and sent back in a 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 new version of a page based on newly generated X-Magento-Vary cookie.

Context Parameters

In order to generate hash value Magento 2 uses parameters which help to differentiate different versions of a 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 are 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 to a different segments e.g. age, total order value in order to increase 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 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 a same page.

magento 2 the devletter

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