Vayu – Open-source, local-first API client and load testing tool

Summary: Vayu is a desktop application combining a modern API debugging UI with a native C++ engine for high-throughput load testing. It operates fully locally without cloud dependencies, supporting scripting compatible with Postman’s pm.test syntax and runs on Windows and Linux.

What it does

Vayu enables visual API debugging and instant stress testing within one tool, using a sidecar architecture that keeps the UI responsive during high-volume request generation.

Who it's for

It is designed for developers needing a privacy-focused, high-performance alternative to Postman and JMeter for API debugging and load testing.

Why it matters

Vayu addresses the lack of modern developer experience in existing load testing tools while ensuring data privacy by avoiding cloud synchronization.