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Criteo OneTag HTTP/HTTPS calls explained


  • Understanding the purpose of the network activity trigger by the Criteo OneTag
  • Understanding the mechanism, 'network flow', of the Criteo OneTag
  • Explaining the reason behind the amount of HTTP calls resulting in pixel injections on my website.

What does the Criteo OneTag do?

The Criteo tags on your site accomplish two important objectives:

  • They collect user browsing data from the pages they are installed on.

We collect information such as what types of pages have been visited by the user (home page, product page, etc.) and what products have been seen. This information allows us to know who to retarget and what to recommend to them.


  • They sync each site visitor with our network of publishers.

The Criteo tags inform selected publishers that we partnered with in order to retarget each of your users offsite (see below point 4 under ‘What calls are triggered by the OneTag ?’). A smart algorithm evaluates where the user can be approached in the most efficient way. As a result, 3rd party http calls may be made. No personal or advertiser-related information is shared with other vendors.


What calls are triggered by the OneTag ?

When our tag fires on one of your pages, it results in a call to our loader and three main HTTP requests. A request from the user's browser to our servers and potentially a couple  HTTP requests to our publisher partner’s ad servers. All requests are asynchronous.

  1. The initial call downloads our main JavaScript library that functions as a framework and prepares all of the following requests.


  1. The second call is the actual tracking event. This event sends the user-browsing information to our servers such as which products are currently being looked at.


  1. The third call request is for inventory selection. This call builds a list of all relevant publishers from our server.


  1. Depending on the result of the inventory selection call, publisher http-calls might be made. This is when publishers are informed that we would like to show ads to the current user whenever he browses the publishers network. These requests are made as image-requests and are therefore also called 3rd party pixels


Read more about the technical details and how Crite ensures that the OneTag is not impacting the website performance: Performance mechanism within Criteo OneTag

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