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Testing · head to head

k6 vs Vitest

k6 logo

k6

Testing

Load testing tool with JavaScript tests on a Go runtime, now owned by Grafana Labs

From
Free
Rated
-
Full reviewWebsite
Vitest logo

Vitest

Testing

Fast unit test framework powered by Vite

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: k6 tests run on a JavaScript engine embedded in Go rather than on Node.js, so npm packages, Node built-ins and existing shared test utilities generally do not work without being bundled to plain JavaScript, and often not even then.; Vitest assumes Vite: projects on webpack or other bundlers lose the main advantage
  • They diverge on capability: k6 covers JavaScript test scripts, Vitest covers Shares Vite config.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which k6 and Vitest actually diverge.

Attributes where k6 and Vitest differ
Attributek6Vitest
PlatformsWindows, macOS, Linux, Docker, KubernetesLinux, macOS, Windows

Identical on both: starting price (Free), pricing model (Open source, no licence fee), free tier (Yes), user rating (Not yet rated), category (Testing).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in k6

  • JavaScript test scripts
  • Thresholds and checks
  • Protocol coverage
  • Browser module
  • Executors
  • xk6 extensions
  • Metrics output
  • Kubernetes operator

Only in Vitest

  • Shares Vite config
  • Jest-compatible API
  • Fast watch mode
  • ESM and TypeScript native

What people use each for

The jobs each tool is most often brought in to do.

k6

  • Gating a deployment pipeline on a threshold such as 95th percentile latency under a defined arrival ratenot Vitest
  • Generating tens of thousands of requests per second from a small number of machines without a load generator fleetnot Vitest
  • Testing gRPC and WebSocket services with the same tooling and thresholds used for HTTP endpointsnot Vitest
  • Correlating a load test against existing dashboards for an organisation already running Grafana and Prometheusnot Vitest

Vitest

  • Unit testing an application already built with Vite, without a second build confignot k6
  • Migrating from Jest for faster watch-mode feedbacknot k6
  • Testing TypeScript and ESM code without transform configurationnot k6

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

k6

  • Tests run on a JavaScript engine embedded in Go rather than on Node.js, so npm packages, Node built-ins and existing shared test utilities generally do not work without being bundled to plain JavaScript, and often not even then.
  • The open source binary runs on a single machine, so distributed load requires the Kubernetes operator or the cloud service, and the operator is infrastructure your team has to run and debug.
  • The AGPL-3.0 licence on the core requires legal review at any company that intends to embed k6 in a product it distributes or offers as a service, which is a slower path than a permissively licensed tool.
  • There is no result storage in the open source tool, so trend history means standing up Prometheus, InfluxDB or Grafana Cloud before load testing produces anything comparable over time.
  • Since the Grafana Labs acquisition the roadmap serves the Grafana observability stack, so a buyer choosing k6 as a standalone tool should expect the standalone experience to receive less investment than the cloud and dashboard integration.
  • Grafana Cloud billing is by virtual user hour, so a long soak test at modest concurrency costs far more than its peak load suggests, and cost planning has to be done in virtual user hours rather than in test runs.

Vitest

  • Assumes Vite: projects on webpack or other bundlers lose the main advantage
  • Younger than Jest, so some plugins and matchers in the Jest ecosystem have no equivalent
  • Jest compatibility is close but not exact, and unusual Jest configurations still need work to port

Pricing, plan by plan

k6

Free
  • k6 OSSFree
    • AGPL-3.0 licence
    • Full test engine, no virtual user limits
    • Runs on one machine unless distributed yourself
  • Grafana Cloud free tierFree
    • Includes a monthly allowance of virtual user hours
    • Hosted test results and dashboards
    • Shared with the rest of the Grafana Cloud free tier
  • Grafana Cloud k6$undefined/month
    • Billed by virtual user hours consumed
    • Load generation from multiple regions
    • Retained test history and comparison

Vitest

Free
  • VitestFree
    • Full functionality
    • Unlimited tests
    • Community support

Which should you pick?

Choose k6 if

  • You need javascript test scripts.
  • You want to start without paying.
  • You work on Windows, macOS, Linux, Docker, Kubernetes.
  • You also want thresholds and checks.
k6 review

Choose Vitest if

  • You need shares vite config.
  • You want to start without paying.
  • You work on Linux, macOS, Windows.
  • You also want jest-compatible api.
Vitest review

Questions people ask

Is k6 or Vitest better?
Neither clearly leads. k6 starts at Free and Vitest at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, k6 or Vitest?
k6 starts at Free and Vitest at Free.
Does k6 or Vitest run on more platforms?
k6 runs on Windows, macOS, Linux, Docker, Kubernetes. Vitest runs on Linux, macOS, Windows.
Can I use k6 for free?
Both have a free tier, so you can try either at no cost before committing.
What is k6 best used for?
k6 is most often used for gating a deployment pipeline on a threshold such as 95th percentile latency under a defined arrival rate, generating tens of thousands of requests per second from a small number of machines without a load generator fleet, testing grpc and websocket services with the same tooling and thresholds used for http endpoints, correlating a load test against existing dashboards for an organisation already running grafana and prometheus. Of those, gating a deployment pipeline on a threshold such as 95th percentile latency under a defined arrival rate and generating tens of thousands of requests per second from a small number of machines without a load generator fleet are not what Vitest is typically brought in for.
What can k6 do that Vitest cannot?
k6 covers JavaScript test scripts, Thresholds and checks, Protocol coverage, Browser module. Vitest covers Shares Vite config, Jest-compatible API, Fast watch mode, ESM and TypeScript native.

Answered from the vendors’ own pages

k6: Can I use npm packages in a k6 test?

Usually not. Scripts run on a Go-embedded JavaScript engine with no Node.js runtime, so packages depending on Node built-ins fail and pure JavaScript libraries must be bundled first.

Vitest: Is Vitest free?

Yes, open source under the MIT licence.

k6: Is k6 free?

The core tool is free under AGPL-3.0 with no virtual user limits. Grafana Cloud k6 is a paid service billed by virtual user hours, with a free monthly allowance.

Vitest: Is Vitest compatible with Jest?

The API is deliberately Jest-compatible and most migrations are mechanical, though unusual configurations and some ecosystem plugins need attention.

k6: Does the Grafana acquisition affect the open source tool?

The tool remains open source and maintained, but investment is directed at making it a data source for Grafana, so standalone use is supported rather than prioritised.

Vitest: Do I need Vite to use Vitest?

It works without a Vite app but the main benefit — sharing one config and transform pipeline — only applies if you are already using Vite.

k6: Can k6 replace a browser testing tool?

No. The browser module measures page-level metrics under load, but functional browser testing belongs in Playwright or a similar tool.

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