Best A/B Testing Tools for Agencies in 2026: Cost Per Client Site

The short answer: For an agency testing across a roster of client sites, Humblytics is the cheapest per client at $79/mo for unlimited sites, which is $7.90 per client at ten clients, and it scores tests in Stripe verified revenue rather than clicks. Crazy Egg is the next cheapest route to testing across many domains at $99/mo with unlimited domains and seats. Convert.com is the strongest mid market pick and explicitly supports multi client projects in one account. VWO, Optimizely and AB Tasty publish no price at all, which is itself a procurement fact. No tool here, Humblytics included, gives you true white label dashboards with per client logins.

An agency buys a testing tool on different terms than an in house team. An in house team has one site, one traffic volume and one budget. You have twelve sites, twelve traffic volumes, and a margin that dies the moment a vendor prices per domain.

So this guide ranks on the two questions that decide it: what the tool costs per client site once you have a roster, and which of your clients has enough traffic to be sold a testing retainer honestly. Every price was read on the vendor's own pricing page in August 2026, with URLs at the end. Where a vendor publishes no number, this guide says so rather than repeating a figure from an aggregator. For the wider agency stack, including heatmap and session replay tools, read best CRO tools for agencies. This page is narrower on purpose: testing platforms only, scored on multi client economics.

At a glance: A/B testing tools by agency economics

Quick verdict

• Cheapest per client site, with revenue scored results: Humblytics
• Cheapest path to testing across unlimited domains: Crazy Egg
• Best mid market platform that expects agencies: Convert.com
• Best for landing page agencies: Unbounce, but only on the Agency plan
• Best for dev led agencies with a warehouse: GrowthBook
• Best for product engineering clients: Statsig
• When a single client funds the contract: VWO, Optimizely or AB Tasty

The three things that decide an agency's testing tool

1. Site and domain caps are the hidden tax

Most vendors price on traffic, and agencies read that as the risk. It usually is not. What quietly destroys agency margin is the domain cap, because it forces you to buy the same product several times.

Unbounce is the clearest example. Its first tier including A/B testing is Experiment at $149/mo monthly or $112/mo annual, covering 2 domains. Ten client sites means five subscriptions, $560/mo, or $56 per client. Unbounce does publish an Agency plan raising the count to 10 domains, but its price is not published. GrowthBook caps projects instead, with 1 on the free plan and 3 on Pro, a hard stop against a ten client roster regardless of what you will pay per seat.

The tools that avoid this are the shortlist. Humblytics covers unlimited sites on its $79/mo plan. Crazy Egg's pricing page states all plans include unlimited website domains and unlimited team members, and that "You will never be charged for having multiple domains or adding more team members to your account."

2. Whether the vendor publishes a price at all

Three of the best known testing platforms will not tell you what they cost until you take a call. Optimizely's pricing page redirects to optimizely.com/plans, publishes no dollar figure, and offers a "Request a demo" CTA under "Customized pricing to your specific needs." AB Tasty publishes no figure either, stating pricing is "based on factors like traffic volume, number of domains, selected modules, and implementation scope." Note the second factor: AB Tasty prices the agency problem directly. VWO lists Growth, Pro and Enterprise with a full feature table but no static price, since the number appears only after you configure monthly tracked users.

For an agency this is not a minor annoyance. You cannot quote a client a tooling line item without a sales cycle, and your cost per client is unknowable until you commit. That is a legitimate reason to disqualify a tool even when the product is good, and all three of these are good.

3. Which of your clients can actually support a test

Many client sites lack the traffic for a test to conclude, and running one anyway produces an inconclusive result you then have to explain. The standard sample size approximation at 95% confidence and 80% power is n per variant = 16 x p x (1 - p) / d squared, where p is the client's conversion rate and d is the absolute lift you want to detect. Worked at a 3% conversion rate:

Run this per client before you scope the engagement. A client producing 300 conversions a month can be sold testing only if the tests are swings of 30% or more, meaning offer changes and page rewrites, not copy tweaks. A client producing 3,000 conversions a month can be sold ongoing incremental testing. Putting the wrong client on the wrong programme is the most common way an agency testing practice loses an account. For clients below the line, sell diagnosis and attribution instead: find which campaigns produce revenue, fix the visibly broken funnel steps, and start testing when the volume arrives.

The 9 best A/B testing tools for agencies in 2026

1. Humblytics

Analytics, click and scroll heatmaps, funnels, no code A/B testing and revenue attribution off one cookie free script, with unlimited sites on every plan. That last detail is the whole agency argument: at $79/mo for 500,000 events across unlimited sites, ten client sites cost $7.90 each.

Attribution is first party UTM based and resolves to a Stripe charge, so a test verdict reads as revenue rather than a conversion rate delta, which is the number a client cares about at retainer review. Tests auto stop at statistical confidence and are not auto promoted, so a winner ships only when someone decides to ship it. A hosted MCP server and REST API let an agent in Claude or Codex read a client's analytics and draft the next test. That is not unique in 2026, since Convert, VWO and PostHog ship MCP servers too. The difference is what the verdict resolves to.

Be clear on the gap. Humblytics does not offer white label dashboards or per client logins, only shareable reports and links. If your pitch depends on a client logging into a portal with your logo on it, this is not that product.

• Price: Business $79/mo (unlimited sites, 500,000 events/mo), Scale from $279/mo (1M events/mo), Enterprise custom, 14-day free trial. Verified August 2026 at humblytics.com/pricing.
• Best for: Agencies running paid traffic to client landing pages who bill on revenue outcomes.
• Limits: No white label, no per client logins, no session replay, no free tier.

2. Crazy Egg

The cheapest legitimate way to get testing running across an unlimited number of client domains. Read the tier boundary first: Starter at $29/mo does not include A/B testing. Unlimited A/B testing begins on Plus at $99/mo, which also covers 150,000 tracked pageviews, 75 heatmap reports and 1,000 recordings a month. Every plan includes unlimited website domains and unlimited team members with role based access control per domain, and the pricing page states that "Any Crazy Egg subscription can support as many clients as needed," alongside flexible agency pricing and free pilots for early clients.

• Price: Starter $29/mo, Plus $99/mo, Pro $249/mo, Enterprise $599/mo, all billed annually. Free plan available. Verified August 2026 at crazyegg.com/pricing.
• Best for: Agencies needing testing on many small client sites at the lowest per client cost.
• Limits: Tracked pageviews pool across all domains, so one high traffic client consumes the allowance. No revenue attribution. Targeting is limited on Plus.

3. Convert.com

The mid market platform that has thought hardest about agency structure, and says so on the page. Its own feature comparison states that "Within Convert, even agencies can add multiple projects to the same account and manage all their clients in an organized way," contrasting this with VWO Workspaces, which it says do not apply to agencies.

Growth is $399/mo monthly or $299/mo billed annually at $3,588 a year. Pro is $599/mo monthly or $420/mo annually at $5,040 a year, adding multivariate and multi page testing, full stack and feature flags, sequential testing and SSO. Both include an MCP server, Convert Heatmaps and Convert Signals, with a 15 day free trial. Watch tested users, not domains: 100,000 a month is shared across your whole roster, and Convert defines tested users as visitors bucketed into experiments, so it is always at or below total traffic.

• Price: Growth $399/mo monthly or $299/mo annual, Pro $599/mo monthly or $420/mo annual, both at 100,000 tested users/mo. Verified August 2026 at convert.com/pricing.
• Best for: Agencies running a real testing practice across several mid sized clients.
• Limits: Roughly four times the per client cost of Humblytics at ten clients. The tested user pool is the ceiling. No white label.

4. Statsig

Experimentation and product analytics with an unusually large free tier. For an agency it fits one client type: SaaS and product companies where the test lives in the application rather than on the marketing page. Not a tool you hand a copywriter.

• Price: Free (2M analytics events, 50,000 session replays, experimentation included), Pro $150/mo (5M events, 100,000 replays), Enterprise custom. Verified August 2026 at statsig.com/pricing.
• Best for: Agencies with product engineering clients.
• Limits: Engineering integration required. No visual editing model.

5. VWO

A deep, mature platform with strong targeting, sitting alongside AB Tasty under common ownership in 2026. Its pricing page lists Growth, Pro and Enterprise with a long feature table but no dollar figure. The number appears only after you set a monthly tracked user volume in its configurator, so every client quote needs a fresh configuration.

• Price: Not published. Configurator based on monthly tracked users. Verified August 2026 at vwo.com/pricing.
• Best for: A single large client with the budget to fund the contract.
• Limits: No published price. Traffic based pricing scales badly across a portfolio.

6. Optimizely

Still the enterprise reference implementation, priced accordingly. The pricing URL redirects to optimizely.com/plans, which publishes no figure. This is a tool you specify for a client buying it themselves, not one you put on your own card and spread across a roster.

• Price: Not published. Demo request only. Verified August 2026 at optimizely.com/plans.
• Best for: Enterprise clients funding their own contract, with you as implementation partner.
• Limits: No published price, enterprise procurement cycle, no agency economics.

7. AB Tasty

Experimentation, personalisation and feature flags, strongest in retail and ecommerce. Pricing is custom and, per the vendor, "based on factors like traffic volume, number of domains, selected modules, and implementation scope." The mention of domain count is the agency relevant detail: adding client sites is a priced variable, not a free one.

• Price: Not published. Custom quote. Verified August 2026 at abtasty.com/pricing.
• Best for: Enterprise retail and ecommerce clients.
• Limits: No published price, and domain count is a pricing input.

8. Unbounce

Workable if your agency builds and tests landing pages rather than client owned sites, but the plan you need is not the one on the pricing table. Starter at $29/mo monthly or $22/mo annual and Build at $99/mo or $74/mo annual both cover 1 domain and neither includes A/B testing. Experiment at $149/mo or $112/mo annual is the first tier with testing, covering 2 domains. Optimize is $249/mo or $187/mo annual with 3 domains. A Concierge tier at 5 domains and an Agency plan at 10 domains exist, neither with a published price. Ten client sites on Experiment means five subscriptions at $560/mo. Get on the Agency plan or do not use it as your roster tool.

• Price: As above, 14-day free trial. Verified August 2026 at unbounce.com/pricing.
• Best for: Landing page agencies on the Agency plan.
• Limits: Domain caps on every published tier. It tests pages you build in Unbounce, not the client's existing site.

9. GrowthBook

Open source experimentation running against your own or the client's data warehouse, with the statistics engine open to inspection. Starter is free with up to 3 users, 1 project and unlimited experiments and traffic. Pro is $40 per seat per month with up to 50 users and 3 projects, plus managed CDN overages at $10 per additional million requests and $1 per additional GB. The project cap is the blocker against a ten client roster. Self hosting removes it, but the managed plans do not scale to an agency portfolio.

• Price: Starter free, Pro $40/seat/mo, Enterprise custom. Verified August 2026 at growthbook.io/pricing.
• Best for: Dev led agencies willing to self host.
• Limits: Project caps on managed plans. Requires a warehouse and engineering time.

What none of these do well: white label

Be direct with clients about this, because vendor marketing pages are not. True white label testing, where the dashboard carries your branding and each client gets an isolated login into their own data, is rare and usually lives behind an enterprise negotiation. Humblytics does not offer white label dashboards or per client logins. It offers shareable reports and links. Crazy Egg offers role based access control per domain, closer to what most agencies need day to day, but that is not white label either.

If white label is a hard requirement, get it in writing and check whether it means custom branding, a separate login per client, or a PDF export with your logo on it. Those three are frequently sold under the same word.

Two more things get implied a lot in this category and should be said plainly. Humblytics auto stops a test at statistical confidence, it does not auto promote the winner, so nothing changes on a client site without a human decision. And it does not flag wasted ad spend. It reports which campaigns produced revenue and leaves the judgement to you.

Choose Humblytics if you

• Test across many client sites and want one flat bill regardless of how many
• Bill on revenue outcomes and need a verdict in dollars, not conversion rate
• Serve EU clients and want cookie consent off your roster wide risk register
• Can work with shareable reports rather than per client portal logins

Choose Convert.com if you

• Run a mature testing practice across several mid sized clients
• Want multi client projects inside one account, which Convert states it supports
• Need multivariate, multi page and server side testing on one platform

Choose an enterprise platform if you

• Have one client large enough to fund the contract on their own
• Are the implementation partner rather than the licence holder
• Can absorb a procurement cycle before you can quote a number

Conclusion

Rank testing tools for an agency in this order: what it costs per client site, whether the vendor will tell you that number without a sales call, and whether your clients have the traffic to make a test conclude.

On the first two, August 2026 published prices put Humblytics at $7.90 per client at ten clients and Crazy Egg at $9.90, with Convert at $29.90 and Unbounce at $56 outside its Agency plan. VWO, Optimizely and AB Tasty publish nothing. On the third, run the sample size math per client before you scope the retainer. The tool is the easy part. Selling a testing programme to a client who cannot support one is the expensive part.

See how revenue scored testing works on the A/B testing page, how revenue attribution resolves a verdict to a Stripe charge, or read the agencies overview.

Frequently asked questions

What is the cheapest A/B testing tool for agencies in 2026?

By cost per client site, Humblytics at $79/mo covering unlimited sites works out to $7.90 per client across ten clients, verified at humblytics.com/pricing in August 2026. Crazy Egg's Plus plan at $99/mo billed annually is next at $9.90 per client, and it also includes unlimited domains and seats. Both beat per domain tools substantially past two or three clients. Crazy Egg's cheaper $29/mo Starter plan does not include A/B testing, so do not budget from that number.

Which A/B testing tools are white label for agencies?

Very few, and the word is used loosely. Humblytics does not offer white label dashboards or per client logins; it offers shareable reports and links. Crazy Egg offers role based access control per domain on all plans. Enterprise platforms sometimes offer branding customisation inside a negotiated contract. Before promising a client a branded portal, get the vendor to confirm in writing whether white label means custom branding, isolated per client logins, or a branded export.

Do VWO, Optimizely and AB Tasty publish their prices?

No, as verified in August 2026. Optimizely's pricing URL redirects to a plans page with no dollar figure and a "Request a demo" CTA. AB Tasty states pricing is custom, based on traffic volume, number of domains, selected modules and implementation scope. VWO lists Growth, Pro and Enterprise with a full feature table but no static price, since the figure appears only after configuring monthly tracked users. Budget a sales cycle before you can quote any of the three.

How much traffic does a client site need for an A/B test to work?

Use n per variant = 16 x p x (1 - p) / d squared at 95% confidence and 80% power, where p is the client's conversion rate and d is the absolute lift you want to detect. At a 3% conversion rate, a 20% relative lift needs about 12,933 visitors per variant, roughly 776 total conversions. A 10% lift needs over 100,000 visitors. A client under about 1,000 conversions a month can only be sold tests of large swings.

Which A/B testing tools show revenue rather than conversion rate?

Humblytics resolves the verdict to a Stripe charge through first party UTM attribution, so a result reads as dollars rather than a conversion rate delta. VWO, Optimizely and Convert can all track revenue goals once the integration is wired up, which is more configuration work but reaches the same place. For an agency billing on outcomes, revenue as the default rather than a setup step is what makes the client review easy.

Can an agent run A/B tests across my client accounts?

An agent can read the data and set tests up, not run your practice. Humblytics ships a hosted MCP server and a REST API so an agent in Claude or Codex can read a client's analytics, heatmaps and funnels and draft a test. It reads everything and changes nothing without you. Convert, VWO and PostHog ship MCP servers too, so agent access is common in 2026 rather than a differentiator. Judge it on what the agent can see and what the verdict resolves to.

Sources

All prices read on the vendor's own pricing page on 17 August 2026.

• Humblytics: https://humblytics.com/pricing
• Crazy Egg: https://www.crazyegg.com/pricing
• Convert.com: https://www.convert.com/pricing/
• Statsig: https://statsig.com/pricing
• Unbounce: https://unbounce.com/pricing/
• GrowthBook: https://www.growthbook.io/pricing
• VWO: https://vwo.com/pricing/
• Optimizely: https://www.optimizely.com/plans
• AB Tasty: https://www.abtasty.com/pricing/