gRPC-Web Browser Client to Standard gRPC Service: Is a Proxy Required?

The goal is to determine whether a browser-based gRPC-Web client can call a standard gRPC service directly over HTTP/2, or whether a translation proxy is mandatory at the integration boundary.

gRPC-Web uses distinct message framing and content encoding compared with canonical gRPC-over-HTTP/2. Native gRPC-Web acceptance, where offered by a server framework, varies by language implementation and release. Streaming RPCs may handle trailers, timeouts, and buffering differently when a proxy mediates traffic.

Assume current major releases of a standard gRPC server in Go, Java, C++, or Node.js, and a browser client using the official gRPC-Web library.

• Does the standard gRPC server require a proxy to translate gRPC-Web frames, or can it accept them natively?
• Is built-in gRPC-Web support stable across the major server language implementations?
• Do streaming RPCs behave differently through a proxy because of trailer and timeout handling?