Testing · head to head
GrowthBook vs KeystoneJS
GrowthBook
Testing
Open source feature flags and A/B testing that run experiment analysis inside your own data warehouse
- From
- Free
- Rated
- -
KeystoneJS
APIs
Powerful Node.js headless CMS framework and API platform
- From
- Free
- Rated
- -
The short version
- Each has a real cost: GrowthBook warehouse-native analysis is only an advantage if you have a warehouse with clean event data in it; without one, GrowthBook has nothing to compute against and you are back to buying an event-collecting platform.; KeystoneJS database support is limited to PostgreSQL, MySQL and SQLite
- They diverge on capability: GrowthBook covers Feature flags, KeystoneJS covers REST API.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which GrowthBook and KeystoneJS actually diverge.
| Attribute | GrowthBook | KeystoneJS |
|---|---|---|
| Pricing model | Per user per month | open-source |
| Platforms | Web, Self-hosted, Docker | Node.js, Self-hosted |
| Category | Testing | APIs |
| Founded | Unknown | 2016 |
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 GrowthBook
- Feature flags
- Warehouse-native analysis
- Reusable metric definitions
- Bayesian and frequentist engines
- CUPED variance reduction
- Visual editor
- Self-hosting
- Guardrail metrics
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.
GrowthBook
- An engineering team that wants feature flags without a per-monthly-active-user bill that grows with product successnot KeystoneJS
- A data team that needs experiment results to reconcile exactly with the metrics reported in its BI toolnot KeystoneJS
- A company with data residency or privacy constraints that cannot send user-level event data to a third-party vendornot KeystoneJS
- Running long-tail experiments where sequential testing and CUPED shorten the time to a decision on low-traffic surfacesnot KeystoneJS
KeystoneJS
- Headless CMS implementationnot GrowthBook
- Content management systemsnot GrowthBook
- Customizable API-driven applicationsnot GrowthBook
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
GrowthBook
- Warehouse-native analysis is only an advantage if you have a warehouse with clean event data in it; without one, GrowthBook has nothing to compute against and you are back to buying an event-collecting platform.
- Metrics are SQL, so a marketing or product team without data engineering support cannot define or fix them, and a badly written metric silently produces a confident wrong answer.
- Cloud Pro bills per seat and then adds CDN request and bandwidth overages, so a high-traffic site can find the variable component exceeds the seat cost it budgeted for.
- Self-hosting means you own the Mongo database, the SDK endpoint availability and the upgrade path, and a flag service that is down is a production incident, not an analytics inconvenience.
- The statistics engine exposes real choices, Bayesian versus frequentist, sequential testing, variance reduction, and the tool will not stop a team that configures them wrongly, so it rewards statistical literacy and punishes its absence.
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
GrowthBook
Free- Open source (self-hosted)Free
- Unlimited users, feature flags and experiments
- One project
- MIT licensed, you run the infrastructure
- Starter (cloud)Free
- Up to 3 users
- 1 project
- Unlimited flags, experiments and traffic
- Pro (cloud)$40/month
- Per seat, up to 50 users
- 3 projects
- CDN overage at $10 per million requests beyond the included allowance
- Enterprise$undefined/year
- Unlimited users and projects
- SSO, audit logs and advanced permissions
- Available on cloud or self-hosted
KeystoneJS
Free- Open SourceFree
- Full KeystoneJS
- Community support
Which should you pick?
Choose GrowthBook if
- You need feature flags.
- You want to start without paying.
- You work on Web, Self-hosted, Docker.
- You also want warehouse-native analysis.
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.
Questions people ask
- Is GrowthBook or KeystoneJS better?
- Neither clearly leads. GrowthBook 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, GrowthBook or KeystoneJS?
- GrowthBook starts at Free and KeystoneJS at Free.
- Does GrowthBook or KeystoneJS run on more platforms?
- GrowthBook runs on Web, Self-hosted, Docker. KeystoneJS runs on Node.js, Self-hosted.
- Can I use GrowthBook for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is GrowthBook best used for?
- GrowthBook is most often used for an engineering team that wants feature flags without a per-monthly-active-user bill that grows with product success, a data team that needs experiment results to reconcile exactly with the metrics reported in its bi tool, a company with data residency or privacy constraints that cannot send user-level event data to a third-party vendor, running long-tail experiments where sequential testing and cuped shorten the time to a decision on low-traffic surfaces. Of those, an engineering team that wants feature flags without a per-monthly-active-user bill that grows with product success and a data team that needs experiment results to reconcile exactly with the metrics reported in its bi tool are not what KeystoneJS is typically brought in for.
- What can GrowthBook do that KeystoneJS cannot?
- GrowthBook covers Feature flags, Warehouse-native analysis, Reusable metric definitions, Bayesian and frequentist engines. KeystoneJS covers REST API, GraphQL API, Admin interface, Node.js.
Answered from the vendors’ own pages
GrowthBook: Is the self-hosted version actually usable, or crippled?
It is genuinely usable: unlimited users, flags and experiments on one project under an MIT licence. The paid tiers add multiple projects, SSO, audit logs and support.
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.
SourceGrowthBook: Do I need a data warehouse?
For experiment analysis, effectively yes. Feature flagging works without one, but the reason to choose GrowthBook over a flag-only tool is the warehouse-native statistics.
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.
SourceGrowthBook: How does the cost compare with LaunchDarkly or Optimizely?
GrowthBook charges per seat rather than per monthly active user or per tracked event, so cost stops scaling with traffic. At high volume that difference is large.
KeystoneJS: Does KeystoneJS offer paid support?
Enterprise support with tailored options is available from Thinkmill, the company behind KeystoneJS. Pricing details available upon request.
SourceGrowthBook: Does it support mobile and server-side flags?
Yes, there are SDKs across JavaScript, React, Python, Go, Ruby, PHP, Java, Kotlin, Swift and more, covering client, server and mobile evaluation.
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