Open source load testing tools: six options reviewed

Six widely used open source load testing tools today are Apache JMeter, k6, Gatling, Locust, Artillery and Vegeta. Choose by the language your team writes tests in and by how you need to scale: JMeter for the widest protocol coverage, k6 or Artillery for JavaScript, Gatling for the JVM, Locust for Python and Vegeta for quick fixed-rate HTTP checks.

We have not benchmarked these tools against each other for this article. The facts come from each project’s own repository and documentation, checked on 8 October 2026, and the “good for” notes are our judgement.

Is Apache JMeter still worth using?

Yes, especially when you need protocols beyond HTTP. JMeter covers the widest range of the six and has the largest body of existing test plans and know-how behind it.

JMeter is a Java application under the Apache 2.0 licence. Its protocol list covers HTTP and HTTPS, SOAP and REST web services, FTP, databases through JDBC, LDAP, JMS messaging, mail and raw TCP. You build test plans in a desktop GUI, run them headless from the command line for real tests, and use the client-server remote mode to spread a test across machines.

Good for mixed-protocol systems, teams with existing JMeter plans and testers who prefer to build tests visually. Choose something else when your team wants tests as plain code that is reviewed like the application, because GUI-built XML plans are hard to read in a pull request.

When is k6 the right choice?

When your team writes JavaScript and wants tests in code with pass/fail thresholds built in. It ships as a single Go binary, which keeps CI setup simple.

k6 is licensed under AGPL-3.0 and speaks HTTP, WebSockets and gRPC, with a browser module for front-end checks. Thresholds turn a goal such as a 95th percentile limit into a non-zero exit code for CI. To scale out, the k6-operator runs distributed tests on Kubernetes, and Grafana sells a hosted service.

Good for developers who keep API tests next to their code, and for CI pipelines. Choose something else when your team does not want JavaScript, or when the AGPL licence conflicts with how you embed or ship the tool. We compare it head to head in k6 vs Artillery.

Who should use Gatling?

Teams on the JVM who want tests as code and a detailed HTML report out of the box. It also offers a JavaScript and TypeScript SDK on the same engine.

Gatling runs virtual users on a non-blocking engine built on Netty, so one machine can drive a lot of load. Simulations are written in Java, Kotlin, Scala, JavaScript or TypeScript and run through Maven, Gradle, sbt or npm plugins. The community edition is Apache 2.0 and covers HTTP/1.1, HTTP/2, WebSocket, Server-Sent Events and JMS, while its gRPC, MQTT and GraphQL components use Gatling’s enterprise component licence.

Good for Java and Scala teams, and for anyone who wants rich reports without extra tooling. Choose something else when you need to spread load across machines from the open source edition alone: generating load from managed or private infrastructure is what the commercial Gatling Enterprise is for.

Is Locust a good choice for Python teams?

Yes. Locust tests are plain Python, so loops, conditions and any Python library work the way they do in ordinary code.

Locust is MIT-licensed and event-based on gevent, which lets a single process handle many users. Tests run from the command line or from a web UI that shows throughput, response times and errors live, and Locust distributes a test across multiple machines on its own. HTTP is built in, and other protocols are added by writing Python.

Good for Python teams, scenarios with complex logic and anyone who likes watching a test in a browser. Choose something else when you want declarative, config-style tests, or when a ready-made plugin for an unusual protocol matters more than writing your own.

When does Artillery make sense?

When your team lives in Node.js, likes short YAML scenarios, or wants Playwright browser tests in the same tool as its API tests.

Artillery is mostly MPL-2.0, with some Azure modules under a source-available licence. It ships with HTTP, WebSocket and Socket.IO, adds gRPC and Kinesis through add-on engines, and its run-lambda and run-fargate commands spread a test across workers in your own AWS account. A run-aci command does the same on Azure Container Instances, with a paid Artillery subscription for anything beyond evaluation (checked on 9 October 2026).

Good for Node.js teams, mixed API and browser testing, and companies already on AWS. Choose something else when you would rather not run Node.js on your load generators, or when large tests have to run outside AWS and Azure.

What is Vegeta good for?

Quick, constant-rate HTTP checks from the command line. It does one job, sending requests at a fixed rate, and keeps that job simple.

Vegeta is an MIT-licensed Go tool that works as a command line program or as a Go library, with a CLI designed to compose with other Unix tools. Because it holds the request rate constant rather than modelling users, it answers questions like “what happens at 500 requests per second” better than it models user journeys.

Good for smoke-checking an endpoint, fixed-rate capacity checks and shell scripts. Choose something else when you need multi-step journeys, think time or detailed reports.

Where does a hosted runner like LoadFocus fit?

None of these tools needs a hosted service, but generating large or geographically spread load from your own machines takes work. A hosted runner takes over the load generation and leaves your scripts as they are.

LoadFocus, the publisher of this site, is one such service. It runs existing JMeter test plans and k6 scripts from 25 cloud regions. It does not run Gatling, Locust, Artillery or Vegeta tests, so for those tools the scaling options above apply. Grafana Cloud k6 and Gatling Enterprise are the vendors’ own hosted routes for k6 and Gatling.

How do you choose between them?

Start from the language your team already writes and the protocols you must test, then check how each tool scales. That usually narrows six options to one or two.

Then write the same short test in your top two choices. Reading both side by side settles most debates faster than any feature table, and our guide on how to run a load test walks through that first test step by step.

FAQ

Which open source load testing tool is the easiest to start with? For a single HTTP endpoint, Vegeta or k6 give you a result within minutes because each is one binary. For multi-step journeys, pick the tool whose test language your team already writes.

Can open source load testing tools run distributed tests? Yes, through different routes: JMeter has a built-in remote mode, Locust distributes across machines natively, k6 uses the k6-operator on Kubernetes and Artillery uses AWS Lambda, Fargate or Azure Container Instances. For Gatling, load generation from managed or private infrastructure is part of the commercial Enterprise edition.

Is JMeter better than k6? Neither is better in general. JMeter covers more protocols and suits GUI-based test design, while k6 suits developers who want tests as JavaScript code in CI.

Related reading

• HTTP benchmarking tools: wrk, hey, oha, ab and more
• Locust load testing: a review of the Python tool
• Gatling load testing: a review of the JVM tool
• WebSocket load testing tools: six options compared
• k6 vs Artillery: which load testing tool fits your team?
• How to run a load test: a step-by-step guide
• Azure Load Testing: a review of Microsoft’s service
• Artillery load testing: a review of the Node.js tool
• NBomber load testing: a review of the .NET framework
• Tsung load testing: a review of the Erlang tool
• pgbench: how to benchmark and load test PostgreSQL
• How to use sysbench for CPU, disk and MySQL benchmarks

The technical claims in this article have not been independently reviewed.