Gostman: a free, open source API clientSend REST, GraphQL, gRPC and WebSocket requests, write tests, run collections in CI, mock APIs and let your coding agent use the same collection. No account, and your data stays on your device. Gostman needs JavaScript to run in the browser.What you get

Requests for REST, GraphQL, gRPC, WebSocket and MCP servers, with environments, auth helpers and a cookie jar

Assertions and scripts, a collection runner with data files, and HTML, JUnit and JSON reports

A command line for CI, a GitHub Action and a Docker image

A local mock server and traffic capture

An MCP server so Claude Code, Codex and Cursor can use your collection without seeing your secrets

Collections stored as plain YAML files you can commit to Git

Import from Postman, Bruno, Insomnia, OpenAPI, HAR and curl

Get Gostman

Download for Windows, macOS and Linux

Open the web app

Source code on GitHub (MIT licence)