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Privacy & Data

Overview of Universal Opt-Out Mechanisms for Web Tracking

Web servers and the entities that operate them have long had the ability to track user agents as they access resources hosted across different web domains. Concern over the privacy implications of such tracking has prompted recent work on a number of solutions that aim to provide a universal opt-out mechanism for web tracking that can be effectuated through a simple binary choice presented to users.

This document provides an overview of the following mechanisms: permanent opt-out cookies, cookie blocking, domain blocking, a “Do Not Track” (DNT) HTTP header, and a Do Not Track Document Object Model (DOM) property. The aim of this document is to describe each approach, the pros and cons of each, and areas where standardization may be necessary should each approach be further pursued, without making recommendations about which approach or approaches should be adopted.