Real-time gRPC traffic viewer — proxy daemon + TUI client.

grpc-tap sits between your application and your gRPC server, capturing every call and displaying it in an interactive terminal UI. Inspect requests, view headers, copy bodies, and replay calls — all without changing your application code.

brew install mickamy/tap/grpc-tap

go install github.com/mickamy/grpc-tap@latest
go install github.com/mickamy/grpc-tap/cmd/grpc-tapd@latest

FROM golang:1.25 AS build
WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 go build -o /usr/local/bin/grpc-tapd ./cmd/grpc-tapd

FROM gcr.io/distroless/static-debian12
COPY --from=build /usr/local/bin/grpc-tapd /usr/local/bin/grpc-tapd
ENTRYPOINT ["grpc-tapd"]

docker build -t grpc-tapd .
docker run --rm -p 8080:8080 -p 9090:9090 \
  grpc-tapd -listen=:8080 -upstream=http://host.docker.internal:9000

git clone https://github.com/mickamy/grpc-tap.git
cd grpc-tap
make install

1. Start the proxy daemon

# Proxy listens on :8080, forwards to upstream gRPC server on :9000
grpc-tapd -listen=:8080 -upstream=http://localhost:9000

2. Point your application at the proxy

Connect your app to the proxy port (:8080) instead of the upstream port. No code changes needed — grpc-tapd speaks native gRPC, gRPC-Web, and Connect protocols.

3. Launch the TUI

grpc-tap localhost:9090

All gRPC calls flowing through the proxy appear in real-time.

grpc-tapd — gRPC proxy daemon for grpc-tap

Usage:
  grpc-tapd [flags]

Flags:
  -listen    client listen address (required)
  -upstream  upstream gRPC server address (required)
  -grpc      gRPC server address for TUI (default: ":9090")
  -version   show version and exit

grpc-tap — Watch gRPC traffic in real-time

Usage:
  grpc-tap [flags] <addr>

Flags:
  -version  Show version and exit

<addr> is the gRPC address of grpc-tapd (e.g. localhost:9090).

┌─────────────┐      ┌───────────────────────┐      ┌─────────────────┐
│ Application │─────▶│  grpc-tapd (proxy)    │─────▶│ gRPC Server     │
└─────────────┘      │                       │      └─────────────────┘
                     │  captures calls       │
                     │  via HTTP/2 proxy     │
                     └───────────┬───────────┘
                                 │ gRPC stream
                     ┌───────────▼───────────┐
                     │  grpc-tap (TUI)       │
                     └───────────────────────┘

grpc-tapd acts as an HTTP/2 reverse proxy that transparently forwards gRPC traffic to the upstream server. It captures request/response headers, bodies, status codes, and timing for each call. Events are streamed to connected TUI clients via gRPC.

• gRPC (HTTP/2, application/grpc)
• gRPC-Web (application/grpc-web)
• Connect (application/connect+proto, application/connect+json)

Press e in the inspector to open the captured request body in $EDITOR as JSON (field numbers as keys). After editing, the modified request is sent to the upstream server via the proxy, and the result appears in the event stream.

MIT