k6

Modern, scriptable load testing with JavaScript; great DX and cloud options.

k6 is a developer‑centric load testing tool that uses JavaScript for scenarios. It offers strong local CLI UX and optional cloud features. Works well in CI/CD.

License	AGPL/OSS
Tags	JavaScript CLI Cloud option
Official site	https://k6.io
GitHub	https://github.com/grafana/k6

When to use

Fits your team’s language and workflows.
Covers required protocols (HTTP, WebSocket, etc.).
Works with CI/CD and observability stack.

Lawful use only

Only test systems you own or have explicit written permission to test. Misuse may be illegal and unethical.