The W3C Technical Architecture Group publishes draft Group Note on web user agents

The W3C Technical Architecture Group (TAG) published a draft Group Note titled Web User Agents on 27 November 2025. The document provides conceptual guidance on the role, duties, and design principles of user agents, which include web browsers and other intermediaries that act between end-users and web content. The draft positions user agents as software that must serve the interests of their users above those of other constituencies, such as content authors, advertisers, or platform providers. The full draft is available on the W3C technical reports page.

The draft Group Note begins by defining web user agents broadly, encompassing traditional browsers as well as tools and intermediaries that fetch, interpret, render, or mediate web resources on behalf of users. It emphasises that, while user agents must implement technical standards, they also embody design choices that can significantly affect user experience, privacy, and security.

A key theme of the draft is the articulation of duties that user agents owe to their users. These include duties of fidelity to user intent, respect for user privacy and security, transparency of operation, and the avoidance of behaviours that prioritise other stakeholders’ interests at the expense of users. The document rejects notions that position user agents primarily as agents of web authors or commercial interests. Instead, it frames user agents as intermediaries whose first obligation is to the individual or organisation operating the software.

The Group Note discusses how these duties can be reflected in the development and implementation of web standards. It highlights scenarios where user agent behaviour affects critical aspects of web interaction, including default privacy settings, handling of cross-origin requests, script execution policies, and interfaces for user consent. The draft does not prescribe specific technical solutions; rather, it outlines principles that should inform both specification authors and implementers when trade-offs arise.

The draft Group Note is intended for a range of audiences. Technical authors who write or maintain specifications may reference the principles when shaping standardised behaviour. User agent developers can use the guidance to align implementations with the articulated duties, particularly in areas where user privacy and security are at stake. Web developers are provided with context for understanding why user agents may enforce constraints that prioritise safety over convenience. The document may also serve as a reference for regulators and policymakers seeking insight into the expectations that the web architecture places on user agent behaviour.

The TAG describes the draft as a conceptual foundation rather than a normative specification. It is presented for community feedback and discussion, with comments and issues welcomed via the document’s GitHub repository. As with other Group Notes, the draft may evolve as the group refines its articulation of principles and responds to stakeholder input.

Read more: The full Web User Agents draft Group Note is available on the W3C website.