Flagsmith vs GrowthBook
An independent, review-free comparison compiled by the SaaSTracker editorial team. Both products are profiled in full, and neither can pay for placement here.
The short answer
Both sides assessedFlagsmith compared with GrowthBook
Both are open source with a free hosted tier, but they draw the line in different places. GrowthBook computes experiment results against your own warehouse with Bayesian and sequential analysis and charges $40 per seat; Flagsmith charges $40 for the whole team at Start-Up but leaves measurement to your analytics vendor. Pick GrowthBook if experiments are the reason you want flags; pick Flagsmith if you want release control and already have analytics you trust.
GrowthBook compared with Flagsmith
Flagsmith is a flag service with no statistics engine at all, priced at $40 a month for a whole three-person team. GrowthBook charges $40 per seat but computes experiment results with sequential testing and CUPED. If you want release control, Flagsmith is far cheaper and does that job well. If you want to know whether the release helped, Flagsmith cannot tell you and GrowthBook can.
Choose Flagsmith if
Engineering teams at small software companies who want a dependable feature flag and remote config service with published pricing that starts at zero, and especially teams who want the option to self-host the same product on their own infrastructure rather than take a hard runtime dependency on a vendor.
Choose GrowthBook if
Product and growth teams at small software companies who already have event data in a warehouse and want to run experiments with defensible statistics, plus engineering teams who want feature flags and the measurement of those flags in the same system without shipping user data to a vendor.
Side by side
13 attributes| Attribute | Flagsmith | GrowthBook |
|---|---|---|
| Category | Product Analytics | Product Analytics |
| Starting price | $0 (Free), then $40 per month billed yearly (Start-Up) (free plan available) | $0 (Starter, 3 seats), then $40 per seat per month (Pro) (free plan available) |
| Pricing model | Freemium subscription metered on API requests per month with a seat cap per tier, plus a free open source self-hosted edition and an Enterprise tier for private or on-premises hosting. | Per-seat subscription on cloud with a free tier, plus a free unlimited-user open source self-hosted edition and quoted Enterprise plans on both. Usage charges apply only to CDN delivery and the optional Managed Warehouse. |
| Free plan | Free covers 50,000 API requests a month for one team member, with unlimited feature flags, environments, identities, and segments plus API access, subject to a fair usage policy. | Starter is free for up to 3 users and 1 project, with unlimited feature flags, unlimited experiments, and unlimited traffic. No credit card required. |
| Free trial | 14 days on Start-Up and Scale-Up | No fixed trial; the free Starter tier and the open source build serve as the evaluation path |
| Best for | Engineering teams at small software companies who want a dependable feature flag and remote config service with published pricing that starts at zero, and especially teams who want the option to self-host the same product on their own infrastructure rather than take a hard runtime dependency on a vendor. | Product and growth teams at small software companies who already have event data in a warehouse and want to run experiments with defensible statistics, plus engineering teams who want feature flags and the measurement of those flags in the same system without shipping user data to a vendor. |
| Setup time | An hour to a first flag in production. Create a project and environments, install the SDK, wrap one code path, and ship. The work that takes longer is deciding on naming conventions and who is allowed to change production. | A day for a first experiment if you already have clean event data in a warehouse. Connect the data source, define two or three metrics, install the SDK, and launch. Without a warehouse, add however long it takes to get events landing somewhere, or use the Managed Warehouse to shortcut it. |
| Learning curve | Low for developers and effectively unavailable to non-developers. The mental model is small: environments hold values, identities carry traits, segments are rules over traits. The subtlety worth learning early is the difference between remote and local evaluation, because it determines both your latency and your bill. | Moderate and front-loaded on metric definition. The flag half is easy; the experimentation half asks you to think about conversion windows, denominators, guardrails, and priors. Teams that skip this get results that look precise and are not. The visible SQL helps, because a data-literate person can check the definition rather than trusting a label. |
| Platforms | JavaScript and React, React Native and Flutter, iOS and Swift, Android and Kotlin, Node, Python, Java and Spring Boot, .NET, Go, PHP, Ruby, Rust, OpenFeature providers | JavaScript and React, Node, Python, PHP, Ruby, Go, Java, C# and .NET, Elixir, Kotlin and Android, Swift and iOS, React Native and Flutter, Cloudflare Workers, Fastly, and Lambda@Edge |
| Compliance | GDPR, Enterprise security review supported; confirm the current SOC 2 and ISO 27001 scope with the vendor during procurement | GDPR posture strengthened by design: only aggregated statistics leave your infrastructure and GrowthBook collects no user data, Self-hosted deployment available behind a firewall for buyers who cannot use a processor at all, Confirm current SOC 2 scope with the vendor during procurement |
| Founded | 2018 | 2020 |
| Headquarters | London, United Kingdom | Anaheim, California, United States |
| Ownership | Bootstrapped, privately held (legal entity Bullet Train Ltd) | Venture-backed, Y Combinator W22 |
Strengths and limitations
Flagsmith
Strengths
- Unlimited flags, environments, identities, and segments on every tier including free, so the plan limit is a request meter rather than an artificial cap on how you model your product.
- A genuine open source self-hosted edition with Docker, Helm, and Kubernetes operator paths, which gives you an exit and satisfies data residency requirements no hosted-only vendor can meet.
- The Edge API is real infrastructure rather than a marketing claim: eight AWS regions, Lambda@Edge, DynamoDB global tables, latency routing, and regional failover.
- Local evaluation in server-side SDKs removes Flagsmith from your request path entirely, which is the correct answer to the availability objection every engineer raises about flag services.
Limitations
- No experiment analysis engine. Flagsmith splits traffic and stops there; there is no sequential testing, no CUPED, no automatic significance calculation, and no guardrail metrics, so measurement lives in another vendor.
- The free tier is limited to a single team member, which means any collaboration at all requires the paid plan regardless of how few requests you make.
- SSO, change requests, role based access control, and audit logs are gated to the $250 Scale-Up tier, a six times price increase over Start-Up for governance features rather than product capability.
- The self-hosted edition is free to license but requires you to run and upgrade Postgres, Redis, and the API, and some enterprise governance features are not in the open source build.
GrowthBook
Strengths
- The statistics engine is genuinely serious: Bayesian by default with configurable priors, a frequentist option with sequential testing, CUPED variance reduction on both, and multiple testing corrections on dimensional breakdowns.
- Every result shows its SQL and exports to a Jupyter notebook, and the engine source is public, which makes results auditable rather than a vendor assertion.
- Warehouse-native architecture means your event data never leaves your infrastructure and only aggregate statistics reach GrowthBook, which shortens the data protection review considerably.
- Six automatic data quality checks including sample ratio mismatch catch the broken experiments that quietly poison decision-making elsewhere.
Limitations
- Per-seat pricing at $40 punishes larger teams; a fifteen-person product organisation on Pro pays $600 a month for capabilities that a smaller team gets for $120.
- You need a data source. Without a warehouse or the paid Managed Warehouse, GrowthBook has nothing to compute against, so it is not a first analytics purchase.
- Metric definition is real work in SQL, and the quality of every result depends on getting conversion windows, denominators, and capping right. There is no autocapture shortcut.
- Project limits are tight: one project on Starter and self-hosted open source, three on Pro, unlimited only on Enterprise.
Pricing compared
Flagsmith
Freemium subscription metered on API requests per month with a seat cap per tier, plus a free open source self-hosted edition and an Enterprise tier for private or on-premises hosting.
- Free$0
- Start-Up$40
- Scale-Up$250
- EnterpriseCustom
- Open source self-hosted$0
At $40 a month for a million requests and three seats, Flagsmith is among the cheapest credible flag services available, and the free tier is a real product rather than a teaser. Modelling a bill is straightforward once you understand the meter. A product with 10,000 monthly users evaluated through server-side SDKs in local evaluation mode generates almost no billed requests at all and sits comfortably on Start-Up at $40. The same product at 100,000 monthly users, evaluated from the browser at a handful of requests per user per month, plausibly lands between 1 and 5 million requests, which means Start-Up plus overage at $50 per million or a move to Scale-Up at $250. The uncomfortable part of the curve is not volume, it is governance: SSO, change requests, and audit logs all sit behind the $250 tier, so a team that needs approvals pays six times more for the same flags. Compared with LaunchDarkly's per-seat and per-connection model the total is usually far lower, and compared with GrowthBook you are paying less but getting no statistics engine.
GrowthBook
Per-seat subscription on cloud with a free tier, plus a free unlimited-user open source self-hosted edition and quoted Enterprise plans on both. Usage charges apply only to CDN delivery and the optional Managed Warehouse.
- Starter (Cloud)$0
- Pro (Cloud)$40
- Enterprise (Cloud)Custom
- Open source (Self-hosted)$0
- Enterprise (Self-hosted)Custom
Judged on statistics per dollar, GrowthBook is the best value in this category by a wide margin: sequential testing, CUPED, proper Bayesian inference with configurable priors, multiple testing corrections, and six automatic data quality checks are all present on a free tier. Judged on total bill, it depends entirely on headcount. Because the meter is seats rather than events, traffic volume barely matters: a product with 10,000 monthly users and one with 100,000 monthly users both cost the same, which is either a bargain or an irrelevance depending on your shape. A five-person team on Pro pays $200 a month; a twenty-person team pays $800, which is where the free self-hosted build with unlimited users starts to look attractive if you have the operational capacity. Against Statsig, whose free tier is enormous and whose statistics are comparably sophisticated, GrowthBook wins on warehouse-native architecture and auditability and loses on out-of-the-box analytics. Against Flagsmith or Unleash it costs more and does far more.
Editorial verdict on each
Flagsmith
Flagsmith is the sensible feature flag purchase for a small engineering team that wants release control without an enterprise contract. Unlimited flags and environments on every tier, a real Edge API across eight regions, local evaluation that keeps the vendor out of your request path, and an open source codebase you can run yourself add up to more infrastructure quality than the $40 a month price suggests. Buy it if your problem is shipping safely: dark launches, percentage rollouts, kill switches, remote config for mobile. Do not buy it expecting experimentation, because the statistics simply are not there and pretending otherwise leads to teams shipping on gut feel with a flag as decoration. Watch two things during evaluation: whether your integration is chatty enough to blow past the request meter, and whether you will need SSO and approvals soon, because that governance jump takes you from $40 to $250 without adding a single product capability.
Read the full Flagsmith profileGrowthBook
InnovationGrowthBook is the experimentation platform to buy if you care whether the numbers are right. Sequential testing, CUPED, configurable Bayesian priors, multiple testing corrections, and automatic sample ratio mismatch detection are present on a free tier, and every result shows the SQL that produced it. That combination does not exist anywhere else at this price. The architecture is the other half of the argument: your data stays in your warehouse, only aggregates leave, and a self-hosted build with unlimited users is always available as an exit. Buy it if you already have event data in a warehouse and a habit, or an ambition, of running real experiments. Do not buy it as a first analytics tool, because it computes against data it does not collect, and do not assume the seat meter is cheap without multiplying $40 by your actual headcount. The work that determines your return is metric definition, and no vendor can do that part for you.
Read the full GrowthBook profileFlagsmith profile last reviewed 2026-08-22; GrowthBook last reviewed 2026-08-22. Pricing is compiled from public sources and can change without notice. See our methodology.