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Testing · head to head

k6 vs KeystoneJS

k6 logo

k6

Testing

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

From
Free
Rated
-
Full reviewWebsite
KeystoneJS logo

KeystoneJS

APIs

Powerful Node.js headless CMS framework and API platform

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.; KeystoneJS database support is limited to PostgreSQL, MySQL and SQLite
  • They diverge on capability: k6 covers JavaScript test scripts, KeystoneJS covers REST API.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which k6 and KeystoneJS actually diverge.

Attributes where k6 and KeystoneJS differ
Attributek6KeystoneJS
Pricing modelOpen source, no licence feeopen-source
PlatformsWindows, macOS, Linux, Docker, KubernetesNode.js, Self-hosted
CategoryTestingAPIs
FoundedUnknown2016

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

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 KeystoneJS

  • REST API
  • GraphQL API
  • Admin interface
  • Node.js
  • Next.js
  • React
  • Databases
  • Node.js support

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 KeystoneJS
  • Generating tens of thousands of requests per second from a small number of machines without a load generator fleetnot KeystoneJS
  • Testing gRPC and WebSocket services with the same tooling and thresholds used for HTTP endpointsnot KeystoneJS
  • Correlating a load test against existing dashboards for an organisation already running Grafana and Prometheusnot KeystoneJS

KeystoneJS

  • Headless CMS implementationnot k6
  • Content management systemsnot k6
  • Customizable API-driven applicationsnot 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.

KeystoneJS

  • Database support is limited to PostgreSQL, MySQL and SQLite
  • Keystone 5 is a separate legacy product documented on a different site and is not covered by the Keystone 6 docs
  • Upgrading requires following a dedicated Migrate to 8.0.0 guide, so major versions are not drop-in
  • Free support is a community Slack; enterprise-grade consulting and support is a separate paid engagement with Thinkmill and no published price

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

KeystoneJS

Free
  • Open SourceFree
    • Full KeystoneJS
    • 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 KeystoneJS if

  • You need rest api.
  • You want to start without paying.
  • You work on Node.js, Self-hosted.
  • You also want graphql api.
KeystoneJS review

Questions people ask

Is k6 or KeystoneJS better?
Neither clearly leads. k6 starts at Free and KeystoneJS at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, k6 or KeystoneJS?
k6 starts at Free and KeystoneJS at Free.
Does k6 or KeystoneJS run on more platforms?
k6 runs on Windows, macOS, Linux, Docker, Kubernetes. KeystoneJS runs on Node.js, Self-hosted.
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 KeystoneJS is typically brought in for.
What can k6 do that KeystoneJS cannot?
k6 covers JavaScript test scripts, Thresholds and checks, Protocol coverage, Browser module. KeystoneJS covers REST API, GraphQL API, Admin interface, Node.js.

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.

KeystoneJS: Is KeystoneJS free?

Yes, KeystoneJS is free and open source with no licensing fees. Core platform has no lock-in and is contributed to by 250+ developers.

Source
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.

KeystoneJS: What are hosting costs for KeystoneJS?

KeystoneJS is self-hosted and deployment-agnostic. Hosting costs depend on your chosen deployment platform (Vercel, AWS, Heroku, etc.) and infrastructure, not KeystoneJS itself.

Source
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.

KeystoneJS: Does KeystoneJS offer paid support?

Enterprise support with tailored options is available from Thinkmill, the company behind KeystoneJS. Pricing details available upon request.

Source
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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