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Testing · head to head

CircleCI vs k6

CircleCI logo

CircleCI

Testing

The leading CI/CD platform

From
Free
Rated
-
Full reviewWebsite
k6 logo

k6

Testing

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

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: CircleCI the free plan covers 6,000 build minutes and 5 active users a month; 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.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which CircleCI and k6 actually diverge.

Attributes where CircleCI and k6 differ
AttributeCircleCIk6
Pricing modelsubscriptionOpen source, no licence fee
PlatformsWebWindows, macOS, Linux, Docker, Kubernetes
Founded2011Unknown

Identical on both: starting price (Free), 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 CircleCI

Nothing recorded that k6 does not also cover.

Only in k6

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

What people use each for

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

CircleCI

  • Continuous integration pipelines for application codenot k6
  • Parallel test execution across containersnot k6
  • Docker-based builds with layer cachingnot k6
  • Deployment pipelines with approval gatesnot k6
  • Self-hosted runners for private infrastructurenot k6

k6

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

Where each one falls short

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

CircleCI

  • The free plan covers 6,000 build minutes and 5 active users a month
  • Active users are billed at $15 each beyond the included five, and an active user is anyone who commits to a project
  • Everything runs on credits, so compute, Docker layer caching at 200 credits a job and IP ranges at 450 credits per GB all draw from the same pool
  • Network and storage overage costs 420 credits per GB
  • Free credits expire monthly with no rollover, and paid credits expire after a year
  • Scale is annual billing only

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.

Pricing, plan by plan

CircleCI

Free
  • FreeFree
    • Up to 6,000 build minutes (small Docker resource class)
    • Up to 5 active users per month
    • 30,000 free credits per month
  • Performance$15/month
    • 30,000 credits included monthly
    • 5 active users included (additional users $15/month each)
    • 80x concurrency
  • Scale$null/year
    • Custom number of credits
    • Customizable user limits
    • Unlimited concurrency

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

Which should you pick?

Choose CircleCI if

  • You want to start without paying.
CircleCI review

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

Questions people ask

Is CircleCI or k6 better?
Neither clearly leads. CircleCI starts at Free and k6 at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, CircleCI or k6?
CircleCI starts at Free and k6 at Free.
Does CircleCI or k6 run on more platforms?
CircleCI runs on Web. k6 runs on Windows, macOS, Linux, Docker, Kubernetes.
Can I use CircleCI for free?
Both have a free tier, so you can try either at no cost before committing.
What is CircleCI best used for?
CircleCI is most often used for continuous integration pipelines for application code, parallel test execution across containers, docker-based builds with layer caching, deployment pipelines with approval gates. Of those, continuous integration pipelines for application code and parallel test execution across containers are not what k6 is typically brought in for.
What can CircleCI do that k6 cannot?
k6 covers JavaScript test scripts, Thresholds and checks, Protocol coverage, Browser module.

Answered from the vendors’ own pages

CircleCI: How much does CircleCI Performance plan cost?

CircleCI Performance plan costs $15 USD per month and includes 30,000 credits, 5 active users, 80x concurrency, 5 GB network, and 2 GB storage. Additional users beyond 5 cost $15 each per month.

Source
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.

CircleCI: Can I purchase additional credits on CircleCI Performance plan?

Yes, additional credits are available at $15 for every 25,000 credits purchased. Paid credits roll over month to month and expire after one year; free plan credits expire monthly without rollover.

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.

CircleCI: What is included in the CircleCI free plan?

The free plan includes up to 6,000 build minutes per month (small Docker resource class), 5 active users, 30,000 free credits monthly, 30x concurrency, 1 GB network, 2 GB storage, and community support. No credit card required.

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.

CircleCI: What are the Scale plan limits and pricing?

CircleCI Scale plan offers custom pricing billed annually with unlimited concurrency, 50 GB network, 200 GB storage, customizable credits and users, enterprise controls, and GPU environment access. Requires contacting sales for a quote.

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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