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Software Development · head to head

Flagsmith vs k6

Flagsmith logo

Flagsmith

Software Development

Open-source feature flag and remote config 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: Flagsmith the Free plan supports only a single team member, limiting collaboration for small teams.; 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.
  • They diverge on capability: Flagsmith covers Feature flags, k6 covers JavaScript test scripts.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Flagsmith and k6 actually diverge.

Attributes where Flagsmith and k6 differ
AttributeFlagsmithk6
Pricing modelfreemiumOpen source, no licence fee
Platformsweb, apiWindows, macOS, Linux, Docker, Kubernetes
CategorySoftware DevelopmentTesting

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 Flagsmith

  • Feature flags
  • Segments
  • A/B testing
  • Scheduled flags
  • SDKs
  • SAML/SSO

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.

Flagsmith

  • Gradual feature rollouts across environmentsnot k6
  • Remote configuration without redeploying codenot k6
  • Running A/B tests tied to feature flagsnot k6
  • Self-hosting feature flags for data residency requirementsnot k6

k6

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

Where each one falls short

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

Flagsmith

  • The Free plan supports only a single team member, limiting collaboration for small teams.
  • Exceeding request limits triggers overage charges after a one-time 30-day grace period.
  • Enterprise-grade SSO and governance are locked behind the Scale-Up and Enterprise tiers.
  • Self-hosting requires operating and updating the platform yourself, unlike a fully managed SaaS competitor.

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

Flagsmith

Free
  • FreeFree
    • Up to 50,000 requests/month
    • 1 team member
    • Unlimited feature flags, environments, identities and segments
  • Start-Up$45/month
    • Up to 1,000,000 requests/month
    • 3 team members
    • Scheduled flags, 2FA, A/B testing, integrations, email support
  • Scale-Up$300/month
    • 5,000,000+ requests/month
    • 5-20 team members
    • SAML/SSO, governance features, priority support

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 Flagsmith if

  • You need feature flags.
  • You want to start without paying.
  • You work on web, api.
  • You also want segments.
Flagsmith 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 Flagsmith or k6 better?
Neither clearly leads. Flagsmith 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, Flagsmith or k6?
Flagsmith starts at Free and k6 at Free.
Does Flagsmith or k6 run on more platforms?
Flagsmith runs on web, api. k6 runs on Windows, macOS, Linux, Docker, Kubernetes.
Can I use Flagsmith for free?
Both have a free tier, so you can try either at no cost before committing.
What is Flagsmith best used for?
Flagsmith is most often used for gradual feature rollouts across environments, remote configuration without redeploying code, running a/b tests tied to feature flags, self-hosting feature flags for data residency requirements. Of those, gradual feature rollouts across environments and remote configuration without redeploying code are not what k6 is typically brought in for.
What can Flagsmith do that k6 cannot?
Flagsmith covers Feature flags, Segments, A/B testing, Scheduled flags. k6 covers JavaScript test scripts, Thresholds and checks, Protocol coverage, Browser module.

Answered from the vendors’ own pages

Flagsmith: What does Flagsmith cost?

Flagsmith has a Free plan, a Start-Up plan from $40-45/month, a Scale-Up plan from $250-300/month, and custom Enterprise pricing.

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.

Flagsmith: Is there a free plan, and what are its limits?

The Free plan supports up to 50,000 requests per month and 1 team member, with unlimited feature flags, environments, identities and segments.

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.

Flagsmith: How is usage metered?

Usage is metered by monthly API requests; exceeding a plan's limit triggers overage charges starting around $50 per million requests, with a 30-day grace period the first time a paid plan exceeds its limit.

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.

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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