Locust

Locust is an open source performance/load testing tool for HTTP and other protocols. Its developer-friendly approach lets you define your tests in regular Python code.

Locust tests can be run from command line or using its web-based UI. Throughput, response times and errors can be viewed in real time and/or exported for later analysis.

You can import regular Python libraries into your tests, and with Locust's pluggable architecture it is infinitely expandable. Unlike when using most other tools, your test design will never be limited by a GUI or domain-specific language.

To get started right away, head over to the documentation.

Features

Write user test scenarios in plain old Python

If you want your users to loop, perform some conditional behaviour or do some calculations, you just use the regular programming constructs provided by Python. Locust runs every user inside its own greenlet (a lightweight process/coroutine). This enables you to write your tests like normal (blocking) Python code instead of having to use callbacks or some other mechanism. Because your scenarios are “just python” you can use your regular IDE, and version control your tests as regular code (as opposed to some other tools that use XML or binary formats)

from locust import HttpUser, task, between

class QuickstartUser(HttpUser):
    wait_time = between(1, 2)

    def on_start(self):
        self.client.post("/login", json={"username":"foo", "password":"bar"})

    @task
    def hello_world(self):
        self.client.get("/hello")
        self.client.get("/world")

    @task(3)
    def view_item(self):
        for item_id in range(10):
            self.client.get(f"/item?id={item_id}", name="/item")

Distributed & Scalable - supports hundreds of thousands of users

Locust makes it easy to run load tests distributed over multiple machines. It is event-based (using gevent), which makes it possible for a single process to handle many thousands concurrent users. While there may be other tools that are capable of doing more requests per second on a given hardware, the low overhead of each Locust user makes it very suitable for testing highly concurrent workloads.

Web-based UI

Locust has a user friendly web interface that shows the progress of your test in real-time. You can even change the load while the test is running. It can also be run without the UI, making it easy to use for CI/CD testing.

Can test any system

Even though Locust primarily works with web sites/services, it can be used to test almost any system or protocol. Just write a client for what you want to test, or explore some created by the community.

Hackable

Locust's code base is intentionally kept small and doesn't solve everything out of the box. Instead, we try to make it easy to adapt to any situation you may come across, using regular Python code. There is nothing stopping you from:

VS Code extension

Microsoft has built an excellent VS Code extension that uses Copilot to help you create and run Locust tests. Here's a video to get you started:

Azure Load Testing

Azure offers a managed load-testing service that lets you run and scale Locust tests easily.

Scalable and flexible, with no need to host your own infrastructure
If your application is hosted on Azure, it can combine test results with detailed resource metrics to help pinpoint bottlenecks and optimize performance.
Integrates well with Azure DevOps and GitHub for CI/CD pipelines, enabling automated performance testing as part of your development workflow.

Authors

Maintainer: Lars Holmberg
UI: Andrew Baldwin
Original creator: Jonatan Heyman
Massive thanks to all of our contributors

Special thanks

Microsoft contributes to and sponsors the continued maintenance of Locust ❤️

License

Open source licensed under the MIT license (see LICENSE file for details).

Release files for locust 2.46.6.dev12

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for locust 2.46.6.dev12
File	Size	Uploaded
locust-2.46.6.dev12.tar.gz	1.5 MB	Sep 17, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for locust 2.46.6.dev12
File	Interpreter	ABI	Platform	Reset
locust-2.46.6.dev12-py3-none-any.whl 1.5 MB Sep 17, 2026	Python 3	none	any	Details

Total release size: 3.0 MB

Release files / locust-2.46.6.dev12.tar.gz

Download URL	locust-2.46.6.dev12.tar.gz
Size	1.5 MB
Tags	Source
SHA-256 checksum How to use checksums	`79bcdc6242ea9cbf5d69106044b5d8bb3e40ebbbefaf1256c779982ba1c76607`
BLAKE2b-256 checksum How to use checksums	`05391ce70be7abf31489e119536b486c27ef4c7a8113ee24d802f1d7470807f5`
Upload date	Sep 17, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/7.0.0 CPython/3.13.14`

Release files / locust-2.46.6.dev12-py3-none-any.whl

Download URL	locust-2.46.6.dev12-py3-none-any.whl
Size	1.5 MB
Tags	Python 3
SHA-256 checksum How to use checksums	`3d71d8662ca36f0b6c4d3548ae396fd081a0175a24b7b8a20c2a47a9164287bc`
BLAKE2b-256 checksum How to use checksums	`5e4f0e69c819fa763baa1588ff2ed9a4a9736903519713c5029a603012a3b0d8`
Upload date	Sep 17, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/7.0.0 CPython/3.13.14`