Description of Working Group The WebTransport working group will define new client-server protocols or protocol extensions in order to support the development of the W3C WebTransport API https://wicg.github.io/web-transport. The WebTransport working group will define a protocol or suite of protocols that support a range of simple communication methods. These must include unreliable messages (that might be limited by the path MTU), reliable messages, and ordered streams of reliable messages. Attention will be paid to the performance of the protocol, in particular protocol overheads and the potential for head-of-line blocking; its ability to be deployed and used reliably under different network conditions; and the ability to integrate protocol use into the Web security model. The group will pay attention to security issues arising from the above scenarios so as to ensure against creation of new modes of attack. To assist in the coordination with W3C, the group will initially develop an overview document containing use cases and requirements in order to clarify the goals of the effort. Feedback will also be solicited at various points along the way in order to ensure the best possible match between the protocol extensions and the needs of the W3C WebTransport API. The group will also coordinate with related working groups within the IETF, such as QUIC and HTTPBIS, as appropriate.