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Testing · head to head

k6 vs Selenium

k6 logo

k6

Testing

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

From
Free
Rated
-
Full reviewWebsite
Selenium logo

Selenium

Testing

Browser automation framework and the W3C WebDriver standard

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.; Selenium flaky tests are the standing complaint: explicit waits and synchronisation are the tester’s job, where newer tools handle it automatically
  • They diverge on capability: k6 covers JavaScript test scripts, Selenium covers W3C WebDriver.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which k6 and Selenium actually diverge.

Attributes where k6 and Selenium differ
Attributek6Selenium
PlatformsWindows, macOS, Linux, Docker, KubernetesLinux, macOS, Windows, Web

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 Selenium

  • W3C WebDriver
  • Many language bindings
  • Selenium Grid
  • Broad browser 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 Selenium
  • Generating tens of thousands of requests per second from a small number of machines without a load generator fleetnot Selenium
  • Testing gRPC and WebSocket services with the same tooling and thresholds used for HTTP endpointsnot Selenium
  • Correlating a load test against existing dashboards for an organisation already running Grafana and Prometheusnot Selenium

Selenium

  • Cross-browser testing where Safari and legacy browsers must be coverednot k6
  • Teams whose test suites are written in Java or C# rather than JavaScriptnot k6
  • Distributing a large suite across a grid of machinesnot 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.

Selenium

  • Flaky tests are the standing complaint: explicit waits and synchronisation are the tester’s job, where newer tools handle it automatically
  • Setup involves drivers, versions and grid infrastructure that Playwright and Cypress bundle away
  • Slower to run than tools that talk to browsers over a debugging protocol rather than WebDriver

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

Selenium

Free
  • SeleniumFree
    • 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 Selenium if

  • You need w3c webdriver.
  • You want to start without paying.
  • You work on Linux, macOS, Windows, Web.
  • You also want many language bindings.
Selenium review

Questions people ask

Is k6 or Selenium better?
Neither clearly leads. k6 starts at Free and Selenium at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, k6 or Selenium?
k6 starts at Free and Selenium at Free.
Does k6 or Selenium run on more platforms?
k6 runs on Windows, macOS, Linux, Docker, Kubernetes. Selenium runs on Linux, macOS, Windows, Web.
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 Selenium is typically brought in for.
What can k6 do that Selenium cannot?
k6 covers JavaScript test scripts, Thresholds and checks, Protocol coverage, Browser module. Selenium covers W3C WebDriver, Many language bindings, Selenium Grid, Broad browser support.

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.

Selenium: Is Selenium free?

Yes, open source with no licence fee. Paid costs come from grid infrastructure or services like BrowserStack.

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.

Selenium: Selenium or Playwright?

Playwright handles waiting automatically and is faster to set up, which removes most flakiness complaints. Selenium wins on language breadth, browser coverage including Safari, and existing suites you already have.

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.

Selenium: Is Selenium still relevant?

Yes. Its WebDriver protocol is a W3C standard implemented by every major browser, and very large existing suites are not rewritten cheaply.

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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