Last Update: June 28, 2021

W3C/WHATWG Relationship update

This document is an update of the Memorandum of Understanding Between W3C and WHATWG, entered May 28, 2019 (“MOU”).

WHEREAS, W3C and WHATWG have been working together collaboratively under the terms of the May 28 MOU;

THEREFORE, W3C and WHATWG wish to memorialize certain additional agreements. All provisions of the MOU continue to apply to the HTML and DOM specifications, and will apply to the MOU Update Specifications (defined below) in the same way that they apply to the HTML and DOM specifications. To the extent these below terms conflict with the MOU, the terms below supersede. All other provisions in the MOU remain the same and remain in effect.

In response to inquiries in the collaborative relationship, WHATWG has instituted a policy under which persons who, for various reasons, are unable to sign the Contributor and Workstream Participant Agreement as an Entity or as an Individual; such persons can now request to be invited.

W3C will transfer the development of the following specifications to WHATWG, where they will be published as WHATWG specifications or components thereof: Web IDL, HTML Media Capture, Worklets, Resource Hints, Preload, Media Playback Quality. Similar to the HTML and DOM specifications, these specifications will be developed principally in the WHATWG, following the WHATWG Working Mode and, in the event of disagreement, the Conflict Resolution process outlined in the MOU shall be followed.

This collaboration will enable proper maintenance of the Web IDL specification and support W3C Working Groups that depend on the Web IDL language to describe their APIs. W3C will discontinue any specification release plans for these specifications, and the Web IDL editors are committed to address issues and resolve pull requests raised by W3C Groups. W3C and WHATWG will continue jointly developing tools to support the Web IDL specification outside the scope of the MOU and MOU Update.

WHATWG will integrate the W3C specifications on HTML Media Capture, Worklets, Resource Hints, Preload, Media Playback Quality in the HTML and DOM specifications. The objective is to consolidate the specification of the elements in the HTML specification rather than having the definition and the specification of the behavior in different documents.

Parties agree to extend the scope of the collaboration process to include (“MOU Update Specifications”):

  1. Specifications that have been newly split from the HTML and DOM specifications, with advance notification to the WHATWG Steering Group;
  2. The Fetch specification (a successor to the CORS specification); and
  3. The Web IDL specification.

W3C shall have the ability, but not the obligation, to endorse these specifications as W3C Recommendations, following the process of §§3-5 in the original MOU (in alternate working groups as necessary).

This MOU Update shall take effect on June 30, 2021 and remain in force until terminated as described herein. Either Party may give notice of intent to terminate this MOU Update, in whole or for particular covered specifications. The terminating Party shall give nine (9) months’ notice, to afford the other Party the opportunity to discuss amended terms for collaboration or adapt its practices to the absence of such collaboration. The Binding Commitments as outlined in the MOU will apply to this MOU Update and survive the termination of this MOU Update.

Future agreements relating to deliverables to be moved or copied between the parties will be recorded in

Patent and Copyright

The provisions in the Patent and Copyright section of the MOU remain in force, and apply to the MOU Update Specifications in the same way they applied to the HTML and DOM specifications as outlined in the MOU. W3C will take best efforts to provide guidance to participants who seek to obtain patent commitments on the identified specifications before specifications are moved to WHATWG, to the extent the specifications are not yet Recommendations.

In addition, W3C confirms that W3C and each of its Hosts grants to anyone, including WHATWG, WHATWG Steering Group Member companies and their employees, and WHATWG specification editors, contributors and implementers, a royalty-free license under the W3C Software and Document Notice and License (version that took effect on May 13, 2015) to reproduce, distribute, create derivative works of, publicly perform and publicly display the following specifications: Web IDL, HTML Media Capture, Worklets, Resource Hints, Preload, Media Playback Quality. Parties confirm that under this MOU Update, WHATWG, WHATWG Steering Group Member companies, and WHATWG editors and contributors will reproduce these specifications within and develop, modify and distribute these specifications through WHATWG’s specification development repositories, websites and resources.

The provisions in the Patent and Copyright section of the MOU and in this MOU Update will survive termination of the MOU Update.