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locustio/locust

Open source load testing tool that lets you define HTTP and other protocol load tests as plain Python code, with a web UI.

Open-source alternative to:LoadRunnerGatling Enterprise

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What is it?

Locust is a performance and load testing tool for HTTP and other protocols. Test scenarios are ordinary Python classes and functions, so you can use loops, conditionals, calculations and third-party libraries, and keep the tests in version control like any other code.

Tests can be run from the command line or through a web-based UI that shows throughput, response times and errors in real time. Results can also be exported for later analysis, and the load can be adjusted while a test is running. Each simulated user runs in a lightweight greenlet, and tests can be spread across multiple machines to drive high concurrency.

Locust works mainly with web services but can be extended to other systems by writing a custom client. Its architecture is pluggable, so custom load shapes and reporting integrations can be added in Python.

Key features

  • 01Write test scenarios as regular Python code with loops and conditionals
  • 02Web UI showing real-time throughput, response times and errors
  • 03Command-line mode suitable for CI/CD pipelines
  • 04Distributed runs across multiple machines for high concurrency
  • 05Change the load level while a test is running
  • 06Extensible to other protocols with custom clients and load shapes

Use cases

  • Load testing a REST or web API before a release
  • Measuring how a service behaves as concurrent users grow
  • Running automated performance checks in a CI pipeline
  • Testing non-HTTP systems by writing a custom Python client

Quick start

  1. 1

    Open the installation guide in the Locust documentation

Topics

#load-testing#performance-testing#python#http#benchmarking#distributed-testing#load-generator#load-test#load-tests#locust

FAQ

What is locust?
Open source load testing tool that lets you define HTTP and other protocol load tests as plain Python code, with a web UI. Locust is a performance and load testing tool for HTTP and other protocols. Test scenarios are ordinary Python classes and functions, so you can use loops, conditionals, calculations and third-party libraries, and keep the tests in version control like any other code.
Is locust free to use? What license does it have?
locust is open source under the MIT license. Check the license terms before using it in commercial products.
Is locust still maintained?
Actively maintained. The last commit to locust was on Oct 24, 2026.
What can I use locust for?
Load testing a REST or web API before a release Measuring how a service behaves as concurrent users grow Running automated performance checks in a CI pipeline Testing non-HTTP systems by writing a custom Python client
How do I install locust?
Open the installation guide in the Locust documentation
Where can I get locust?
The source code and installation instructions are on GitHub: https://github.com/locustio/locust

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