K6 Vs. Gatling


When it comes to evaluating the performance and scalability of web applications, two well-known open-source load testing tools stand out: K6 and Gatling. These tools enable developers and testers to simulate heavy user loads and analyze their systems’ reactions to stress.


K6 is a popular open-source tool that focuses on the needs of developers. It is specifically designed for load-testing web applications and APIs. With K6, developers can write performance tests using JavaScript, gaining valuable insights into system performance under different loads. The tool strikes a balance between simplicity and flexibility, making it a favorite among developers and DevOps teams for load testing and performance monitoring.


Gatling is another remarkable open-source load-testing tool that excels in evaluating the performance and scalability of web applications, APIs, and other systems. Developed using advanced technologies such as Scala, Akka, and Netty, Gatling offers exceptionally high performance through its asynchronous and event-driven architecture. Its commendable scalability, user-friendly interface, and robust reporting capabilities set Gatling apart. Developers, testers, and DevOps teams extensively employ Gatling to verify the performance and scalability of their applications.

Differences between K6 and Gatling:

1) Language and Scripting:

K6 utilizes JavaScript as its scripting language, providing a user-friendly and developer-oriented scripting interface. On the other hand, Gatling is coded in Scala and employs a specialized language called Gatling DSL. While Gatling’s DSL is robust, individuals unfamiliar with Scala may find it more challenging to learn.

2) Ease of Use:

K6 prioritizes simplicity and ease of use, offering a user-friendly command-line interface (CLI) and providing clear and concise documentation. Its scripting syntax is straightforward, facilitating efficient script creation, and it benefits from a strong community support network. Gatling’s DSL may appear complex to beginners due to its intricate nature, but it compensates for this with a wide array of features and customization options. Additionally, Gatling offers a user-friendly web-based interface for script creation and configuration.

3) Architecture:

K6 is designed with a clear and easy-to-understand architecture, focusing on developers’ needs. It uses lightweight threads called Virtual Users (VUs) in its single-process architecture. On the other hand, Gatling is constructed using Scala and features an asynchronous and event-driven architecture. It employs an Actor-based concurrency model, enabling efficient handling of high volumes of concurrent users.

4) Scripting Capabilities:

K6 enables the creation of complex scenarios through scripting, supporting modern JavaScript syntax and offering built-in functions for tasks such as making HTTP requests, handling cookies, setting headers, and managing authentication. It also supports scripting with multiple virtual users and protocols like WebSocket and server-sent events (SSE). Gatling provides its own DSL, offering a powerful scripting capability for creating intricate scenarios. Its DSL includes a fluent API for defining HTTP requests, assertions, and session management. Gatling also supports advanced features such as dynamic data feeding, session handling, and data extraction from responses.

5) Protocol Support:

Both tools support various protocols like HTTP, HTTPS, and WebSocket. However, Gatling goes a step further by providing additional protocol capabilities like JMS and JDBC, making it a viable option for testing messaging systems and databases.

6) Reporting and Metrics:

K6 generates real-time test execution metrics and offers a wide range of performance metrics, including response time, throughput, error rate, and latency. It produces customizable HTML and JSON reports that can be easily integrated with other reporting tools. Gatling also generates detailed HTML reports with various performance metrics such as response time distribution, requests per second, and error rate.


In deciding between K6 and Gatling it is important to consider your specific requirements, familiarity with the languages, and the level of complexity needed for performance testing. K6 is often preferred for its simplicity, JavaScript scripting, and developer cantered approach. On the other hand, Gatling is recognized for its scalability, advanced features, and extensive reporting abilities.

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You can also check our blog on Performance Testing using JMeter