Locust - A modern load testing framework
An open source load testing tool. Define user behaviour with Python code, and swarm your system with millions of simultaneous users.
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Locust is an open-source load testing tool that lets you define user behaviour in Python code and simulate millions of simultaneous users.
🚀 Overview
Locust is a Python-based tool for writing scalable load tests in plain code, allowing you to simulate realistic user interactions on web applications and other systems.
It solves the problem of performance testing under heavy load by enabling developers to create flexible, code-driven test scenarios instead of relying on rigid GUI tools or XML configurations. Locust supports distributed testing across multiple machines, making it possible to simulate millions of users effortlessly.
Built for developers, DevOps engineers, and QA teams working on web apps and HTTP services, Locust was created to provide a simple yet powerful alternative for battle-tested load testing—as used by companies like EA/DICE for Battlelog.
✨ Key Features
- Define user behaviour in code: Write test scenarios directly in Python—no clunky UIs or DSLs needed—which makes tests readable, versionable, and easy to extend.
- Distributed & scalable: Run tests across multiple machines using gevent for event-based async I/O, simulating millions of simultaneous users.
- Web-based UI: Real-time monitoring dashboard to view stats, adjust load, and spawn/stop users dynamically.
- Flexible task system: Assign weights to tasks for realistic simulation, add wait times with
between(), and use nested TaskSets for modular tests. - Optional: Plugins for custom protocols, integrations like Grafana, TimescaleDB, and a hosted cloud version at locust.cloud.
🛠 Tech Stack
- Language: Python (with gevent for asynchronous execution)
- Web UI: Built-in for monitoring
- CLI: locust command
- Extensible: Plugins and custom clients
- Hosting: Self-hosted or distributed across machines
👥 Who Is This For?
This project is useful for:
- Developers who want to load test web apps programmatically
- Teams looking for scalable performance testing without proprietary tools
- Indie makers and enterprises building high-traffic services
📸 Screenshots / Demo
- Live demo: https://docs.locust.io/en/stable/
- GitHub: https://github.com/locustio/locust
🔥 Project Status
- 🟢 Actively building
Last updated: 2026-03-24
❓ FAQ
Is this project free?
Yes / Open Source (The core tool is completely free and open source under MIT license; commercial hosted version available at locust.cloud.)
Is the source code available?
Yes — https://github.com/locustio/locust
Can I contribute?
Yes—check GitHub issues, submit PRs, join discussions at https://github.com/orgs/locustio/discussions, or chat on Slack (https://locustio.slack.com).
📬 Contact & Links
- Website: https://locust.io
- GitHub: https://github.com/locustio/locust
- Documentation: https://docs.locust.io
- Slack: https://locustio.slack.com (invite: https://communityinviter.com/apps/locustio/locust)
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