k6 vs Gatling
k6 and Gatling are both code-first load testing tools built for CI. k6 is a Go binary that runs JavaScript scripts with thresholds that fail the build; Gatling runs simulations written in Java, Kotlin, Scala, JavaScript or TypeScript on the JVM. Choose k6 for a JavaScript team on Grafana; choose Gatling for a JVM team or the Enterprise Edition dashboards.
- k6
- Grafana Labs' load testing tool: a single Go binary that runs JavaScript scripts from the command line with pass or fail thresholds.
- Gatling
- A code-first load testing tool with SDKs for Java, Kotlin, Scala, JavaScript and TypeScript, an open-source engine and a paid Enterprise Edition.
How do k6 and Gatling compare?
| Dimension | k6 | Gatling |
|---|---|---|
| Scripting language | k6JavaScript, executed inside the k6 binary rather than in Node | GatlingJava, Kotlin, Scala, JavaScript or TypeScript through fluent SDKs |
| Runtime | k6A single binary written in Go | GatlingThe JVM for the Java, Kotlin and Scala SDKs; a JavaScript SDK for Node projects |
| Protocols | k6HTTP/1.1, HTTP/2, WebSockets, gRPC; more through xk6 extensions | GatlingHTTP, WebSocket, Server-Sent Events, JMS, gRPC and MQTT officially |
| Pass or fail in CI | k6Thresholds and checks are first class; the run exits non-zero when a threshold fails | GatlingAssertions on the simulation fail the build; Enterprise adds SLO tracking and stop criteria |
| Browser-level testing | k6The k6 browser API drives Chromium and collects browser metrics | GatlingProtocol level; no browser rendering |
| Distributed load | k6Grafana Cloud k6, or the k6 operator on Kubernetes | GatlingCommunity Edition is local only; distributed load generation is an Enterprise Edition feature |
| Reporting | k6End-of-test summary; time series exported to Grafana, Prometheus and others | GatlingA static HTML report per run in Community; live dashboards, history and trends in Enterprise |
| Recording | k6k6 Studio desktop app and a HAR converter | GatlingRecorder and HAR file import |
| Licence and cost | k6Open source, AGPL; cloud execution is paid | GatlingOpen source engine, Apache 2.0; Enterprise Edition is paid |
When should you choose k6, and when Gatling?
Choose k6 when
- The team writes JavaScript and wants a tool with no JVM in the toolchain.
- You already run Grafana and want load test metrics next to the system metrics.
- You need browser-level checks alongside protocol-level load in one script.
- The AGPL licence is acceptable for how you use it.
Choose Gatling when
- The team writes Java, Kotlin or Scala and wants load tests in the same build as the application.
- You need JMS or MQTT without building a custom binary.
- The organisation will pay Enterprise Edition for run history, comparisons and distributed execution.
- You prefer an Apache 2.0 licence on the engine.
How does k6 vs Gatling come up in QA interviews?
This pairing comes up in engineering-led teams that have already rejected GUI tools. Interviewers want to see that you can express a load model as code, wire it into CI with a pass or fail gate, and explain what the results do and do not prove.
- 01How would you express a ramp to 500 virtual users over five minutes, hold, and ramp down, in k6 and in Gatling?
- 02What is a k6 threshold, and what is the closest Gatling equivalent for failing a build?
- 03Your load test needs to run from three regions. How does each tool get you there, and what does it cost?
- 04What does a protocol-level load test miss that a browser-level test would catch?
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Common questions about k6 vs Gatling
Is k6 or Gatling better?
They solve the same problem for different teams. k6 suits JavaScript teams and Grafana users and includes a browser API. Gatling suits JVM teams and offers official JMS and MQTT support plus a paid Enterprise Edition with dashboards. Pick by language and by where you want the results to live.
Does Gatling support JavaScript?
Yes. Gatling provides a JavaScript and TypeScript SDK alongside the Java, Kotlin and Scala SDKs, so a Node.js team can write simulations without the JVM toolchain in their project.
Can k6 or Gatling run distributed tests for free?
k6 can, through the open-source k6 operator on Kubernetes; Grafana Cloud k6 is the paid route. Gatling Community Edition runs on one machine, and distributed load generation is part of the paid Enterprise Edition.
Which one do interviewers expect?
Neither specifically. Performance interviews expect JMeter knowledge most often and treat k6 or Gatling as a plus. Being able to explain a load model, thresholds and result analysis matters more than which of the two you have used.
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