If the browser supports http/2, why does grpc-web require envoy proxy?
Is it just required for older browsers that do not support http/2?
Answered in https://github.com/grpc/grpc-web/issues/347. For gRPC-Web to work, we need a lot of the underlying transport to be exposed to us but that's not the case currently cross browsers. We cannot leverage the full http2 protocol given the current set of browser APIs.