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 Data Protection Officer

Weighted verdict

Has to answer whether the test script may run before the consent banner is answered, and usually finds the vendor has not said. Wants the storage keys listed, a documented consent-pending mode, visitor data processed in the EU, and a published subprocessor list that includes the CDN.

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

Scored by The Data Protection Officer

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 Data Protection Officer

Feature-flag experiments, a visual editor, URL redirects and inline server-side tests run through 24+ SDKs across server, client, mobile and edge, with mutual exclusion via namespaces, holdouts, sticky bucketing and a Cloudflare edge app that evaluates flags and rewrites variations before HTML reaches the browser. We found no public information on a personalisation capability that can itself be tested against a control, a documented experiment lifecycle from hypothesis to archived result, or a searchable library of past results. 1 6 7 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 Data Protection Officer

Both engines are documented by name — Bayesian by default with an improper uninformative prior and a switchable proper prior, frequentist two-sample t-tests for relative percent change — alongside Holm-Bonferroni and Benjamini-Hochberg corrections across goal metrics and variations, sample ratio mismatch detection, CUPED on both engines, guardrail metrics, minimum-data checks against reading results too early, and the whole implementation open source under MIT so a result can be reproduced. The captured pages do note that adjusted p-values are available in the interface and CSV downloads but not through the API. 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 Data Protection Officer

The gbuuid cookie is named, first-party and configurable, assignment is documented as stateless hashing that needs no cookie, an environment variable delays writing the cookie until a consent event fires from the page, and sticky bucketing is documented as consent-gated — yet from these pages I still cannot answer whether the exposure tracking callback or the payload fetch waits for the consent banner, and we found no public information on consent-management-platform integrations, cookie lifetimes, IP anonymisation, or guidance on the legal basis for testing in the EU. The privacy notice further states that DNT signals are not responded to or honored. 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 Data Protection Officer

The documentation is candid that the edge app's default is a blocking API call that delays page delivery, and publishes two elimination paths — a webhook push model to an edge key-value store and a just-in-time payload cache — plus CDN delivery of SDK payloads, a proxy server with caching for self-hosters, and edge evaluation that runs visual and redirect experiments into the HTML before it ships to cut flicker. We found no public information on absolute script size figures or measured Core Web Vitals impact. 1 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 Data Protection Officer

Warehouse-native is the core promise: metrics defined once in SQL and computed in the customer's own Snowflake, BigQuery, Databricks or Redshift with every query visible and no PII leaving the warehouse, alongside a full REST API covering experiments, per-experiment results, fact tables and saved groups, and named integrations including Segment.io, GA4, Google Tag Manager, Slack and Shopify. We found no public information on stated API rate limits or streaming export of raw event data. 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 Data Protection Officer

The contracting entity is GrowthBook, Inc. of Anaheim, California, the privacy notice states personal information is held and processed in the United States by consent-through-use, hosting is on AWS, and I found no public information on an EU residency option for the cloud service, on a published subprocessor list that includes the CDN at cdn.growthbook.io, or on server regions for the named AI sub-processors (Anthropic, Google, OpenAI, xAI) and the ClickHouse managed warehouse. Self-hosted, air-gapped deployment is the only documented path that keeps data on infrastructure the customer controls. 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 Data Protection Officer

Starter is free with up to 3 users and 1 project, Pro is "$40 / seat / month" with up to 30 users and 3 projects, and the usage-based pieces carry published limits and overage — managed warehouse events 1M/mo and 2M/mo "then $30/M", CDN requests 1M/mo and 2M/mo "then $10/M", CDN bandwidth 5GB/mo and 20GB/mo "then $1/GB" — with unlimited feature flags, experiments and traffic. Enterprise is priced only as Custom, and we found no public information on minimum term or VAT treatment. 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 →