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gRPC Mock APIs

Upload a .proto file and mock service methods with realistic JSON payloads over an HTTP gRPC-compatible surface.

Try it live

Create a gRPC project

  1. Open New Project.
  2. Click Using GraphQL, gRPC, or SOAP? and select gRPC.
  3. Name the project and create it. gRPC projects start empty.
  4. On the project page, open Import and choose gRPC.
  5. Paste or upload your .proto file. Preview services and methods (unary, client streaming, server streaming), then import.

Each RPC method becomes an endpoint. Paths follow the standard gRPC form /package.Service/Method (package omitted when the proto has no package).

Call a method

Methods are invoked with HTTP POST and JSON bodies using application/grpc+json:

bash

Unary methods return a single JSON object. Server-streaming methods return a streamed response of mock chunks.

json

Test in the app

On a gRPC project, the tester shows a gRPC panel: method path, streaming badges when applicable, and a JSON request body. Send the request to exercise the mock without leaving the project page.

What works today

Supported
  • Unary RPCs with JSON request/response
  • Server-streaming methods (simulated stream chunks)
  • Client-streaming methods marked on import and in the tester
  • Mock data generated from message types
  • API token auth when enabled on the project
Limitations
  • Traffic uses HTTP + application/grpc+json, not native binary gRPC over HTTP/2
  • Method paths are global by package/service/method — use distinct packages when mocking multiple services
  • The project is locked to gRPC after the first endpoint

Importing a .proto into a REST (or other) project fails with HTTP 409. Create a dedicated gRPC project. See Choosing a Protocol.

Try it

Interactive gRPC exampleOpen Builder
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