Conversion Optimization

GrowthBook

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Panel rating · 6 judges · How to read the stars

Category median

Sovereignty: 1 of 4 dimensions proven

0–5 in half steps. 5 means the rubric's top anchor is met on the evidence.

An AI-assisted analysis of public evidence — not a hands-on test.

Every score, rationale and verdict on this page is AI-generated. Every claim cites the source it was read from. Nothing here is a human star review — and no score can be bought. How scores are made →

Method and versions

The Growth Lead v1.0 · The E-Commerce Manager v1.0 · The Product Engineer v1.0 · The CRO Consultant v1.0 · The Data Protection Officer v1.0 · The Skeptic v1.0 · rubric v1 · evaluated 5 Oct 2026

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Read this page as one judge. Each weighs the same scores by what they care about.

The Product Engineer

Weighted verdict

Ships experiments behind feature flags and would rather not ship a third-party script at all. Wants server-side SDKs for the stack in use, edge delivery, metrics computed in the warehouse the team already trusts, and an API good enough to build internal tooling on.

Same scores as the panel view — this lens weights them the way this judge cares.

Scored by The Product Engineer

Experiment types & delivery

How this is scored

What can be tested and where: client-side changes through an editor, server-side and feature experiments through SDKs, multivariate and multi-page tests, and personalisation — judged on what the documentation shows rather than on the feature grid.

0 — Simple A/B split of one page element through a visual editor; no server-side option, no targeting beyond URL.

3 — Client-side A/B and split-URL tests with basic audience targeting, and no SDK or server-side delivery.

5 — Client-side and server-side experiments through documented SDKs for common languages, multivariate and multi-page tests, audience targeting on behaviour and attributes, and rule-based personalisation.

8 — Feature-flag-based experiments sharing one audience and metric model with web tests, mutually exclusive experiment groups, holdouts, edge or CDN delivery, and personalisation that can itself be tested against a control.

10 — One experimentation programme across every surface: web, app, server and edge from the same platform, experiment interactions managed, a documented experiment lifecycle from hypothesis to archived result, and a library of past results a team can search.

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The Product Engineer

Experiments are defined on feature flags and delivered through 24+ SDKs across server, client, mobile and edge, with inline server-side tests that need no third-party requests, mutual exclusion through namespaces, holdouts, sticky bucketing, bandits and multivariate tests, and visual and URL-redirect tests that can be evaluated at the edge before HTML ships. That is most of a modern programme from one platform. We found no public information on personalisation that can itself be tested, or on a documented lifecycle from hypothesis to archived result with a searchable library of past experiments, which is what holds this below the top of the scale. 1 6 7 11 12

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Statistical method & guardrails

How this is scored

Which statistics decide the winner and what protects the customer from misreading them. Scored on what the vendor documents: the method by name, how peeking and multiple comparisons are handled, and whether sample ratio mismatch is detected.

0 — A "winner" or "probability to beat" figure with no documented method, no stated sample-size guidance and no warning against stopping early.

3 — The method is named (frequentist or Bayesian) but its assumptions are not documented, and nothing prevents a test from being called while it is still underpowered.

5 — Documented method with confidence or credible intervals, a sample-size or test-duration calculator, and stated guidance on when a result may be read.

8 — Sequential testing or an equivalent documented protection against peeking, correction for multiple metrics or variants, sample ratio mismatch detection, variance reduction such as CUPED, and guardrail metrics that can stop a harmful test.

10 — The statistics are auditable: methodology published in enough detail to reproduce a result, the choice of method explained per use case, raw per-visitor data available for independent re-analysis, and the interface refuses to present an underpowered result as a conclusion.

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The Product Engineer

Both engines are documented down to the mechanics — a Bayesian default with an improper prior you can switch for a proper Normal prior, two-sample t-tests for relative change on the frequentist side, and your choice of Holm-Bonferroni or Benjamini-Hochberg correction with the test family spelled out. Guardrails are real: CUPED on both engines, sample ratio mismatch detection, multiple-exposure and suspicious-uplift checks, guardrail metrics, power analysis and minimum data requirements so an early read cannot be dressed up as a conclusion. The implementation is open source and every query is visible SQL in your own warehouse, so a result is reproducible; the gaps are small — corrections exist only for the frequentist engine, and adjusted p-values come out in the UI and CSV rather than through the API. 6 7 8 9

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Consent & visitor tracking

How this is scored

Whether the test script respects §25 TDDDG and the ePrivacy rules as evidenced on the vendor's own pages: when the script runs relative to consent, what it stores on the device, whether a cookieless or consent-free mode exists, and how visitor identifiers are handled.

0 — Nothing on the vendor's pages says what the script stores on the device or whether it runs before consent; consent is described as the customer's problem.

3 — Cookies or local storage are listed, and a consent integration is mentioned, but the documentation does not say what the script does before consent is given.

5 — Documented behaviour before and after consent, integration with common consent management platforms, a published list of cookies and storage keys with their lifetime, and IP anonymisation described.

8 — A documented consent-pending mode that holds tracking until consent while variants can still be served, a cookieless or first-party-only option, retention of visitor data stated, and guidance on the legal basis for testing in the EU.

10 — Built for §25 TDDDG: the default configuration stores nothing on the device without consent, a server-side or cookieless mode documented end to end, per-visitor data deletable on request, and the vendor states in writing how each mode maps to consent requirements.

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The Product Engineer

The mechanics are genuinely consent-aware: assignment is stateless consistent hashing so variants serve with no cookie at all, a documented setting defers writing the first-party visitor cookie until consent, a custom event triggers persistence once consent is given, and sticky bucketing can be enabled per visitor only when consent is observed. Against that, the visitor cookie is persisted on page load by default, the privacy notice states Do Not Track signals are not honored, and we found no public information on consent management platform integrations, cookie lifetimes, or IP anonymisation. 3 6 11 12

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Snippet performance & flicker

How this is scored

The cost the client-side snippet imposes on the page it tests: blocking load, flicker of original content, script weight and the effect on Core Web Vitals — scored on what the vendor measures and publishes, not on "lightning fast".

0 — A synchronous snippet with no stated size, no flicker handling and no mention of performance.

3 — An anti-flicker snippet that hides the page until the test loads, with a timeout, and no published figures for script size or load cost.

5 — Script size and loading behaviour documented, asynchronous loading option, flicker handling explained with its trade-off, and CDN delivery of the snippet.

8 — Published performance figures including impact on Core Web Vitals, a self-hosting or first-party-domain option for the script, per-project bundles containing only active experiments, and a server-side or edge alternative for flicker-sensitive tests.

10 — Performance is a stated commitment: measured overhead published and maintained, flicker eliminated by edge or server-side rendering as a documented path, and tooling that shows the customer what their own configuration costs the page.

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The Product Engineer

The edge path is documented end to end — flags and visual experiments evaluated on the edge so variations ship before the browser paints, URL redirects without flicker, SDK injection with a hydrated payload so the front-end makes no extra network calls — and the docs are unusually honest that the default edge setup makes a blocking payload fetch per request, with two documented ways to remove it: a webhook push into an edge key-value store or a just-in-time payload cache. Self-hosters can run the proxy on their own CDN, and SDK endpoints are scoped to a project and environment. We found no published figures for script weight or Core Web Vitals impact, which is what keeps this from scoring higher. 1 5 11 12 14

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Analytics, data export & integrations

How this is scored

Getting results and raw data out: integration with analytics and tag management, export of visitor-level results, warehouse-native analysis, and an API — because an experiment result that cannot be checked in the customer's own data is a claim, not a finding.

0 — Results visible in the vendor's dashboard only; no export, no analytics integration, no API.

3 — CSV export of aggregated results and one analytics integration, with no visitor-level data and no documented API.

5 — Integrations with common analytics and tag managers, export of results, and a documented API for managing experiments and reading results.

8 — Visitor-level raw data export or streaming to a data warehouse, warehouse-native analysis on the customer's own metrics, CDP integration for audiences, and an API with stated limits.

10 — The platform treats the customer's warehouse as the source of truth: metrics defined once and computed there, full historical experiment data exportable in open formats, and a versioned API a team can build its own programme tooling on.

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The Product Engineer

This is the model I want: metrics are SQL against Snowflake, BigQuery, Databricks or Redshift, every query is visible and reproducible, no personal data leaves the warehouse, and results are computed in the warehouse the team already trusts rather than in a black box. The REST API is versioned and deep enough to build internal tooling on — create experiments, toggle features from a deploy script, pull the latest analysis into your own reporting, define fact metrics, segments and saved groups — with webhooks and an MCP server on top. We found no public information on stated API rate limits or CDP integrations. 5 7 13 14

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European sovereignty

How this is scored

Where visitor data is processed and stored and who the contracting entity is. Independently sourced by the sovereignty pipeline; weighted higher here than in categories that hold only the customer's own data, because the script runs on every visitor to the customer's site and their behaviour is what the platform records.

0 — Non-EU vendor and contracting entity, hosting unstated, subprocessors unnamed, and visitor data leaving the EU without a stated safeguard.

3 — EU data residency offered as an option or an enterprise add-on while the contracting entity is non-EU, or the subprocessor list is absent.

5 — EU processing of visitor data as standard and an EU contracting entity, but parts of the chain — CDN, support access, analytics — are non-EU without an explained safeguard.

8 — EU hosting on named infrastructure including the delivery of the snippet, EU contracting entity, subprocessor list published, and a DPA covering the visitor data the script collects.

10 — Sovereign end to end and evidenced: vendor, entity, hosting, snippet delivery and every subprocessor European, certification published, and no visitor data reaching a non-EU party at any point.

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The Product Engineer

Hosted is American end to end: a California entity with Santa Clara venue, AWS hosting, a privacy notice that says information is held by providers in the United States and asks users to consent to transfer and processing there, US AI providers as subprocessors, and website terms offering the service only to persons located in the United States. The escape hatch is real and documented — full self-hosting including air-gapped deployment, and warehouse-native mode where no personal data leaves your infrastructure — but the contracting entity is a California company, and we found no public information on EU data residency for the hosted service or a data processing agreement covering the visitor data the script collects. 3 4 5 14

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Pricing transparency

How this is scored

A category priced by traffic — monthly tracked users, visitors or impressions — where the tier a site lands in depends on numbers the buyer has to estimate. Whether a buyer can compute the real annual cost including traffic limits, overage, server-side or personalisation modules and seats — from public pages alone.

0 — No public prices at all; every tier is a sales conversation.

3 — A starting price or a free tier exists, but the traffic metric, the limits and what happens above them are unstated — the invoice is unknowable.

5 — Tier prices public with the traffic metric and its limits defined, but at least one commonly needed piece (server-side SDKs, personalisation, overage) is unpriced or "contact sales".

8 — Every tier priced publicly with the traffic metric defined, limits, overage rates, module prices, minimum term and VAT treatment stated.

10 — Complete price computability: annual invoice derivable for a given traffic volume, set of modules and team size, with overage and every add-on published.

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The Product Engineer

Seat pricing with published usage ceilings and overage rates makes the cloud invoice derivable: Starter is free, Pro is $40 / seat / month for up to 30 users, CDN requests are 2M/mo (then $10/M), bandwidth is 20GB/mo (then $1/GB), and the managed warehouse is 2M events/mo (then $30/M), with experiments and feature flags unlimited on every plan. Enterprise is a sales conversation, and we found no public information on minimum term or VAT treatment, so full annual computability stops at the Pro tier. 2 7

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European sovereignty — proven facts

1 of 4 dimensions proven

Built only from facts shown on the vendor's own pages. A dimension we could not prove is left open, not scored as zero.

Legal entity	Not determined	—	uncited Report an error
Ownership	Not determined	—	uncited Report an error
Data residency	Not determined ⚠ unverified	—	uncited Report an error
Subprocessors	US CLOUD Act reach ⚠ unverified	0/2 pts	5 Report an error

Where this could be wrong

Evidence ages. The oldest capture behind this page is from 22 Sep 2026. Vendors change pricing and policies without notice; every fact reflects its source as of the capture date shown in the registry.
Weak sourcing — Data residency. Not confirmed on the vendor’s own pages as captured.
Weak sourcing — Subprocessors. The privacy notice also names US AI providers (Anthropic, Google, OpenAI, xAI) as sub-processors for optional AI features, and the managed warehouse stores event data on 'ClickHouse infrastructure', all without stated server regions.
AI can misread a source. Extraction and judgement are automated; a citation guarantees traceability, not infallibility. If something here is wrong, say so — no account needed, every report is decided within 5 business days, and accepted corrections are published.

What we left out

A claim that does not survive our checks costs us the claim, not the page. This is what was taken off this one.

17 product facts could not be confirmed on the vendor’s page as captured and were left out of this page and of the panel’s material. Know more? Tell us
5 integrations facts could not be confirmed on the vendor’s page as captured and were left out of this page and of the panel’s material. Know more? Tell us
3 legal facts could not be confirmed on the vendor’s page as captured and were left out of this page and of the panel’s material. Know more? Tell us
3 pricing facts could not be confirmed on the vendor’s page as captured and were left out of this page and of the panel’s material. Know more? Tell us
2 compliance facts could not be confirmed on the vendor’s page as captured and were left out of this page and of the panel’s material. Know more? Tell us
1 support fact could not be confirmed on the vendor’s page as captured and was left out of this page and of the panel’s material. Know more? Tell us
1 sovereignty dimension could not be confirmed on the vendor’s own pages and is shown as unknown. Know more? Tell us

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Sources (14)

The pages every claim on this page was read from — each one checked, dated, and kept verifiable.

1 Vendor homepage www.growthbook.io Checked 22 Sep 2026 Details →
2 Pricing page www.growthbook.io Checked 22 Sep 2026 Details →
3 Privacy policy www.growthbook.io Checked 22 Sep 2026 Details →
4 Terms of service www.growthbook.io Checked 22 Sep 2026 Details →
5 Security / trust page www.growthbook.io Checked 30 Sep 2026 Details →
6 Experiment types & delivery — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →
7 Experiment types & delivery — found from sitemap www.growthbook.io Checked 1 Oct 2026 Details →
8 Statistical method & guardrails — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →
9 Statistical method & guardrails — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →
10 Consent & visitor tracking — found from sitemap www.growthbook.io Checked 1 Oct 2026 Details →
11 Snippet performance & flicker — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →
12 Snippet performance & flicker — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →
13 Analytics, data export & integrations — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →
14 Analytics, data export & integrations — found from sitemap docs.growthbook.io Checked 1 Oct 2026 Details →