grpcui vs protoc-gen-doc

grpcui is a free, open-source command-line tool for interacting with gRPC servers through a browser-based interface. It is aimed at gRPC APIs rather than REST APIs and can discover service schemas through server reflection, .proto source files, or compiled protoset files. Its interface builds dynamic forms for protobuf messages, including well-known types, oneofs, and maps, and also accepts a complete JSON request body. grpcui supports RPC methods including streaming, then displays response headers, messages or errors, trailers, and readable HTML tables. It connects to plaintext and TLS servers, including mutual TLS with client certificates. Streaming requests have a constraint: they must be constructed all at once, so bidirectional streams cannot be handled interactively like they can with grpcurl. The project also provides Go packages for embedding a form or complete web UI in a Go HTTP server. Installation is documented through Homebrew on macOS or Linux, and through the Go install command. It is released under the MIT license.

protoc-gen-doc is a documentation generator plugin for the Google Protocol Buffers compiler. It turns comments in .proto files into HTML, JSON, DocBook, or Markdown documentation, covering files, messages, fields, services and methods, enums and values, and extensions. It supports proto2 and proto3, including both in the same context. You can exclude files with path patterns and omit comments marked with the @exclude prefix. The plugin runs through protoc with the --doc_out and --doc_opt options; its source_relative flag places generated output in the same relative directory as the input. For customization, users can supply a Go template or use a stylesheet.css file to change HTML appearance. Installation options include Go, prebuilt releases, a Docker image, and a Maven Central package. It runs on Linux, macOS, and Windows and is self-hosted. The project is free under the MIT License, which allows use, modification, distribution, sublicensing, and sale under its terms. The license provides the software as is, without warranty.