Why React app can't call gRPC?
When we hear about it, it sounds like it should work. gRPC runs on HTTP/2. Browsers speak HTTP/2. So the React app should be able to call the gRPC backend directly, right? It can’t. And the reason isn’t a setting or a flag. It’s the protocol. Why the browser can’t Two reasons, and both are real. First, trailers. gRPC sends its status code at the end of the response, in HTTP trailers, not the headers. grpc-status and grpc-message arrive after the body. That’s fine for a normal gRPC client, but the browser fetch and XMLHttpRequest APIs never expose trailers to your JavaScript. You literally cannot read the thing gRPC uses to tell you the call succeeded or failed. ...