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Locust vs k6: What are the differences?

Locust and k6 are both popular open-source load testing tools used for testing the performance and scalability of web applications. While they share some similarities, there are key differences between Locust and k6 that make each tool unique in its own way.

  1. Programming Language: One of the major differences between Locust and k6 is the programming language they are written in. Locust is written in Python, making it more accessible to developers with Python expertise. On the other hand, k6 is written in JavaScript, which can be advantageous for developers who prefer working with JavaScript or have existing JavaScript codebases.

  2. Architecture: The architecture of Locust and k6 also differs. Locust follows a distributed master-worker architecture, where a master node distributes tasks to multiple worker nodes. This architecture allows for distributed load testing across different machines. On the other hand, k6 follows a single-process architecture, where it runs on a single machine, utilizing all available CPU cores efficiently.

  3. Scripting Approach: Locust and k6 have different approaches to scripting load tests. Locust uses an imperative approach, where the test scripts are written as classes and methods to define user behavior and task execution. On the other hand, k6 uses a declarative approach, where the test scripts are written using JavaScript modules and functions to define HTTP requests and scenarios.

  4. Metrics and Reporting: The way Locust and k6 handle metrics and reporting also differs. Locust provides a basic web UI for monitoring and reporting test results, which can be extended using custom code. In contrast, k6 offers an extensive set of built-in metrics and a powerful console output for live monitoring during the test. It also supports exporting test results to various formats like JSON, InfluxDB, and Grafana.

  5. Integration and Extensibility: Both Locust and k6 support integrations with various external tools and services, but their approaches differ. Locust provides a wide range of official and community-supported integrations, including popular tools like Jenkins, Slack, and Grafana. On the other hand, k6 offers a rich JavaScript API and extensibility through modules, allowing users to integrate with any system or service using JavaScript libraries and frameworks.

  6. Ease of Use: The ease of use of Locust and k6 also varies. Locust, being written in Python, appeals to developers familiar with Python and offers a more Pythonic API. However, developers without Python experience may find the learning curve steeper. In comparison, k6's JavaScript-based scripting and its modern syntax make it more approachable for developers with JavaScript experience and those from web development backgrounds.

In summary, Choose Locust for Python expertise, distributed testing, and custom reporting, while k6 shines for JavaScript familiarity, single-machine efficiency, and rich built-in metrics. Both offer unique strengths for different testing needs.

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Pros of k6
Pros of Locust
  • 13
    Fits nicely in a CI workflow
  • 11
    Test scripts are written in javascript
  • 11
    It's code-first
  • 11
  • 10
    Easy to use
  • 15
  • 11
    Supports distributed
  • 7
    Open source
  • 6
    Easy to use
  • 6
    Easy to setup
  • 4
  • 2
    Test Anything

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Cons of k6
Cons of Locust
  • 3
    Requires bundling and transpiling to use npm packages
  • 1
    Bad design

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What is k6?

It is a developer centric open source load testing tool for testing the performance of your backend infrastructure. It’s built with Go and JavaScript to integrate well into your development workflow.

What is Locust?

Locust is an easy-to-use, distributed, user load testing tool. Intended for load testing web sites (or other systems) and figuring out how many concurrent users a system can handle.

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What companies use k6?
What companies use Locust?
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What tools integrate with k6?
What tools integrate with Locust?

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What are some alternatives to k6 and Locust?
Gatling is a highly capable load testing tool. It is designed for ease of use, maintainability and high performance. Out of the box, Gatling comes with excellent support of the HTTP protocol that makes it a tool of choice for load testing any HTTP server. As the core engine is actually protocol agnostic, it is perfectly possible to implement support for other protocols. For example, Gatling currently also ships JMS support.
It is a hiring platform that provides an affordable way for small businesses to get a handle on their hiring process—a seamless set of features to create custom job posts and application forms, manage incoming candidates, and document the entire journey.
JavaScript is most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic,and supports object-oriented, imperative, and functional programming styles.
Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.
GitHub is the best place to share code with friends, co-workers, classmates, and complete strangers. Over three million people use GitHub to build amazing things together.
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