The browser does have a UDP data stream available for applications to send arbitrary bytes over UDP; it's part of WebRTC.
While Web RTC is built on UDP, it does not allow sending arbitrary UDP. It's DTLS, perhaps encapsulating SCTP, and DCEP.
While Web RTC is built on UDP, it does not allow sending arbitrary UDP. It's DTLS, perhaps encapsulating SCTP, and DCEP.