Protocol Buffers 59,573 (protobuf), Google's internal format since 2001, open-sourced in July 2008 under a BSD license, is the message format of gRPC. It compiles a .proto file into classes for each language and tags every field on the wire, so a reader needs no writer's schema. This section runs protoc 36.2 (17 September 2026; github.com/protocolbuffers/protobuf (https://github.com/protocolbuffers/protobuf 72,089 )) with the Python runtime protobuf 7.36.2; code generated by protoc 36.2 needs runtime 7 or newer.