Earlier this week, Microsoft announced experimental support for gRPC-Web with .NET Core. The new addition allows Blazor WebAssembly clients to call gRPC applications directly from the browser, enabling gRPC features such as server streaming to be used by browser-based applications.
Similarly to gRPC, gRPC-Web uses pre-defined contracts between the (web) client and backend gRPC services. It allows the creation of an end-to-end gRPC pipeline compatible with HTTP/1.1 and HTTP/2 - which is particularly relevant since browser APIs can't call gRPC HTTP/2.
It is also important to notice that not all gRPC features are supported (i.e., client streaming and bi-directional streaming). Using gRPC-Web for .NET requires .NET Core 3.1.