- Agency A/B testing has unique requirements: multi-client management, per-client billing, client-facing reports, and white-label options — most tools designed for single-brand teams handle these poorly.
- Varify.io supports unlimited client projects on every plan, with separate tracking per client, GA4 integration per property, and a dedicated agency partner program — from €149/mo flat-rate regardless of client count.
- The three agency pricing traps: per-client fees (cost scales with client count), MTU aggregation (all clients' traffic pooled into one bill), and seat-based pricing (every team member across all clients counts).
- This guide compares 8 tools on the criteria that agencies — not single-brand teams — actually care about: client management, billing flexibility, collaboration, and GDPR compliance across jurisdictions.
Running A/B tests for one brand is straightforward. Running tests for 5, 10, or 30 clients simultaneously is a completely different operational challenge. You need separate tracking per client, isolated reporting, flexible billing, and a platform that doesn't charge you more for every new client you onboard.
Most A/B testing tools are built for in-house teams optimizing a single website. They work fine when there's one domain, one GA4 property, and one team. But agencies need tools that scale across clients without scaling costs proportionally — and that's where most platforms fall short. This guide evaluates tools specifically from an agency operator's perspective.
What agencies need from an A/B testing tool
Agency requirements differ from in-house teams in five specific ways that most tools don't address:
1. Multi-client project management. You need separate environments per client: isolated experiments, separate tracking codes, independent reports. Some tools charge per project/workspace. Others let you create unlimited projects on one account. The cost difference across 10+ clients is enormous.
2. Pricing that doesn't scale with client count. If the tool charges per workspace, per domain, or aggregates all clients' traffic into one MTU pool, your costs grow faster than your agency revenue. Flat-rate or per-seat models are far more predictable for agencies.
3. Client-facing reporting. Your clients need to see results without accessing your full account. This means exportable reports, shareable dashboards, or separate client logins with restricted access.
4. Collaboration across teams. Account managers, CRO consultants, designers, and developers all need different access levels. Role-based permissions prevent accidents and keep client data isolated.
5. GDPR compliance across jurisdictions. If you serve clients in Germany, France, and the UK, your testing tool needs to handle GDPR for all of them. EU-hosted, cookie-free tools simplify this enormously — instead of configuring consent and DPAs per client, the platform is compliant by default.
8 A/B testing tools for agencies compared
| # | Tool | Multi-client support | Agency pricing | Client reports | Agency score |
|---|---|---|---|---|---|
| 1 | Varify.io | Unlimited projects | from €149/mo flat | GA4 per client | 9.2/10 |
| 2 | Convert | Multi-domain | from $299/mo (tested users) | Shareable reports | 8.0/10 |
| 3 | VWO | Sub-accounts | Custom (MTU pooled) | Dashboard sharing | 7.5/10 |
| 4 | AB Tasty | Multi-project | Custom | Client dashboards | 7.2/10 |
| 5 | Kameleoon | Multi-project | Custom (€15K+/yr) | Custom reports | 6.8/10 |
| 6 | Optimizely | Per-project pricing | Custom ($15K+/yr) | Limited sharing | 6.2/10 |
| 7 | GrowthBook | Multi-org (Cloud) | $40/seat per org | Limited | 5.5/10 |
| 8 | PostHog | Multi-project | Event-based (pooled) | Dashboards only | 5.0/10 |
Source: Claude Research, May 2026. Agency scores based on multi-client management, pricing predictability, client reporting, collaboration features, and GDPR compliance across clients. Pricing from official documentation.
Varify.io — built for agencies from the ground up
Varify.io's agency model solves the three biggest agency pain points: client isolation, predictable costs, and compliance at scale.
What makes Varify work for agencies:
- Unlimited client projects on every plan. Create a separate project per client with isolated tracking, independent experiment lists, and per-project GA4 integration. No per-project fees, no per-domain surcharges.
- Flat-rate pricing regardless of client count. From €149/mo (Growth, 5 active experiments) or €249/mo (Pro, unlimited experiments). Whether you manage 3 clients or 30, the price is the same. Compare that to VWO (MTU across all clients) or Convert ($299 per 100K tested users across all domains).
- GA4 integration per client. Each client's experiments send data to their own GA4 property. Your clients see test results in their existing analytics — no new dashboard to learn, no data leaving their ecosystem. See the analytics integration.
- GDPR-compliant for all clients by default. Hosted in Frankfurt, cookie-free, no consent banners. When you onboard a new German, French, or Austrian client, there's no GDPR configuration — it's compliant out of the box. Full GDPR details.
- Visual editor + code mode. Your CRO consultants use the visual editor for quick tests. Your developers inject custom JS for complex experiments. Both in the same interface.
Learn about the agency partner program →
3 pricing traps agencies fall into
Trap 1: Per-client MTU pooling. VWO and similar tools pool all clients' traffic into one MTU meter. If you manage 10 clients with 50K visitors each, that's 500K MTU — pushing you into an enterprise pricing tier. Your tool cost scales with your clients' collective traffic, not with the value you deliver.
Trap 2: Per-seat pricing across clients. GrowthBook Cloud at $40/seat seems affordable. But if you have 3 CRO consultants, 2 developers, and each of your 10 clients wants their own login, that's 15+ seats = $600+/mo — and you need a separate organization per client. LaunchDarkly's seat pricing has the same multiplication problem.
Trap 3: Annual enterprise commitments. Kameleoon and Optimizely often require 12-month contracts at €15K–50K+/year. For an agency, that's a fixed cost you carry even if you lose clients. Monthly plans (Varify, Convert) let you scale costs with your actual client roster.
The ideal agency pricing: Flat-rate per agency account, not per client, not per user, not per visitor. Varify is the only tool in this comparison that charges one flat price regardless of how many clients, domains, or visitors you manage.
How to evaluate A/B testing tools as an agency
Use this framework when assessing any platform for agency use:
Cost per client. Take the total annual tool cost and divide by your client count. If that number exceeds what you charge the client for testing, the tool is too expensive. With Varify at €249/mo (Pro) and 10 clients, your tool cost per client is ~€25/mo. With VWO at custom pricing for 500K pooled MTU, that number can be 10× higher.
Client onboarding time. How long does it take to set up a new client? Creating a project, installing the snippet, connecting GA4, and inviting collaborators should take under 30 minutes. Tools that require sales calls, contract amendments, or DNS changes per client slow down your operations.
Client offboarding clean-up. When a client leaves, can you delete their project and data completely? GDPR requires this. Tools with shared tracking or pooled data make clean offboarding harder.
White-label potential. Some agencies present the testing tool as part of their own service. Check whether client-facing elements (reports, dashboards, emails) can be customized or at least neutrally branded.
GDPR per-client complexity. If each new client requires a separate DPA, consent configuration, or data residency setup, that's hours of legal work per onboarding. EU-hosted, cookie-free tools (Varify) eliminate this entirely.
Manage all your clients' A/B tests — one platform, one price.
Varify.io: unlimited projects, flat-rate pricing, GDPR-compliant for all clients.