API that allows web applications to establish interactive, bidirectional, multiplexed network connections

It fills gaps in the web platform:

• Lack of UDP-like networking API
• Lack of WebSocket-like API without head-of-line blocking

It provides:

• Reliable streams
• Unreliable datagrams
• Encryption and congestion control
• An origin-based security model
• Bindings for QUIC
• Multiplexing with existing HTTP/3 connections
• Flexible API that can be extended to other protocols, such as TCP fallback and p2p
• Ability to change transport without changing application code

It's great for:

• sending or receiving high-frequency, small messages that don't need to be reliable (like game state)
• sending or receiving low-latency media
• transferring files

See the explainer for more info.

See the proposed spec.