ConversionWise tops our list of the best A/B testing agencies in the UK for 2026. Compare 10 agencies on testing method, variant builds and who each suits.
Written by
Oliver Kenyon
Co-Founder & CEO
ConversionWise tops our list of the best A/B testing agencies in the UK for 2026. Compare 10 agencies on testing method, variant builds and who each suits.
I've compared 10 UK A/B testing agencies on how they plan experiments and how much of each variant their own team builds.
Every profile also points to the type of business that tends to get the most out of working with that agency.
The best A/B testing agency in the UK is ConversionWise, as we run testing programmes for DTC brands where strategy, design, copy and development all happen in-house, and every winning variant is measured on revenue per visitor.
Here’s our shortlist of the 10 best vendors in the market:
Every agency here names A/B testing as a service on its own website and works with UK clients.
To rank them, I looked at four things:
ConversionWise helps DTC brands grow revenue after the ad click, and A/B testing is how our programmes prove which changes to offers and pages deserve to stay live.
Strategists, designers, copywriters and developers all work in-house at ConversionWise, meaning a test can go from brief to live variant without leaving our team.
Brands usually get in touch with us after one of these experiences:
Programmes work in monthly cycles, and the first experiment is always the one with the biggest likely effect on revenue.
Convert.com is our main testing platform, and ConversionWise holds Premium Agency Partner status there.
💡 If your team already pays for VWO or a similar tool, we run the programme inside it.
Revenue per visitor is the number every ConversionWise report is built around.
Conversion rate alone can mislead, since a variant that converts more shoppers at a smaller basket size might leave total sales unchanged.
Page layout is only one part of what our team tests for clients. Our programmes also cover:
💡 Before committing to a test, you can run your own numbers through our free A/B Test Revenue Calculator, which estimates the annual value of anything from a 3% to a 10% lift.
Below roughly 100,000 monthly sessions, most stores cannot run an A/B test to statistical significance in a reasonable number of weeks.
For those brands, our team skips the split test and ships the improved page directly, using evidence from comparable stores, then tracks revenue against the period before launch.
Testing is added to the programme once traffic grows enough to support it.
Programme size depends on the tier: Foundation clients usually have one or two build-first workstreams on the go, while the Growth and Optimisation tiers run builds and tests side by side, scaling up to several parallel workstreams on full testing infrastructure.
Our in-house AI, Optimo, learned from 13 years of ConversionWise experiments and page builds across more than 4,000 ecommerce brands.
Strategists use it at two points: early on, to spot friction and rank hypotheses by expected revenue impact, and later, to prototype variants faster.
Losing and inconclusive tests are fed back into the model too, because a failed idea on one store is useful evidence for the next.
Clients never get a login or a separate invoice for Optimo.
It informs our strategists, and the decision on what to test is still made by a person who understands your margins and trading calendar.
We have official partnerships with Shopify, Convert.com (Premium Agency Partner), Heatmap.com and WooCommerce support our testing work, and clients have given ConversionWise a verified 4.9 rating across more than 350 five-star reviews.
Here are some of our results:
Retainers begin at $3,000 a month, and there's no onboarding fee or minimum term, only 30 days' notice if you decide to stop.
Our target is to get the first change live within 10 days of onboarding.
💡 The Six-Month Commitment works like this: we pick one metric with you at the start, and if six months pass without it moving, the pod keeps working at no extra cost.
You can book a free discovery call to go through your traffic and testing setup, and to agree on where a first experiment would make the biggest difference.
Found adds A/B and multivariate testing to a digital marketing offer built around SEO and PPC, giving brands one team for traffic and on-site performance.
Testing work begins with research into where shoppers stall on the site, and those findings set the order of the first experiments.
Impression's CRO team runs its experiments in VWO, the platform it names as its main technology partner for conversion work.
Hypotheses are drawn from analytics and user research, giving each test a reason to exist before any design work starts.
abtests.co.uk is the experimentation consultancy of Stafferton Digital, working mainly with ecommerce and property brands.
Its selling point is statistical honesty, so sample sizes and success criteria are fixed before launch, and nobody calls a winner from an early spike in the data.
Behavioural science shapes Reflect Digital's test hypotheses, drawing on psychology, neurolinguistics and audience profiling to explain why visitors hesitate.
Clients range from charities to B2B firms, and programmes typically open with client workshops and user testing before any tests go live.
Eskimoz is a search and performance marketing group with a CRO team that runs A/B and multivariate tests, reporting the results in the Eskimoz App next to each client's search and paid media data.
Hypotheses are ranked before launch according to expected conversion impact, using the client's analytics and behavioural data as evidence.
For ecommerce brands turning over between $500k and $50M, Searchflex sells A/B testing as part of CheckoutOS, a package that covers the journey from first click to checkout.
Test ideas come from analytics and UX research on the store, and the team reports each result against revenue and average order value.
Boutique agency SOMO feeds its A/B test findings directly into the paid media and organic campaigns it runs for clients.
Findings are used to adjust landing pages and campaign decisions, with the aim of turning more paid clicks into sales and leads.
A/B testing and landing page development are sold together at Move Ahead Media, a digital marketing agency that also manages SEO and Google Ads campaigns.
Tests pit two landing page designs against each other, usually changing the copy or the call to action to see which version converts better.
Romax provides AB Testing in Marketing for direct mail and multichannel campaigns, aimed at organisations that send printed or digital communications to large member and customer databases.
A share of each mailing goes to control cells, giving the team a baseline to measure new creative against before the strongest version is sent to the rest of the list.
The right A/B testing agency is one whose testing method suits your traffic and whose team can build and launch the variants it recommends.
These points are worth raising on a first call:
Almost every A/B testing agency in the UK covers research, hypothesis planning, test builds and reporting.
The bigger differences show up in statistical discipline and in whether the agency designs and develops variants or only recommends them.
Depending on the agency, a testing programme can involve:
💡 Proprietary tools also differ between agencies: ConversionWise uses Optimo, its in-house AI, while abtests.co.uk runs experiments on its own ABexis platform.
When tests keep ending inconclusive, or winning variants never show up in monthly revenue, the programme around them is usually what needs fixing.
Our first priority is the change most likely to raise your revenue, and the target is to have it live within 10 days.
On a free 30-minute discovery call, a strategist will go through your store and numbers and explain where our team would begin.
If the numbers suggest a programme would cost more than it returns at your current traffic, the strategist will say so on that call.
Brands turning over less than £1M a year tend to get better value from Conversion Rate Academy, our training programme, which more than 10,000 students have taken since 2022.
ConversionWise is the best A/B testing agency in the UK for DTC brands, running monthly testing programmes measured on revenue per visitor.
Offers and pricing are tested alongside page design, and for SketchWow those winning tests added $156,000 in monthly revenue.
For Shopify and Shopify Plus stores, the best choice is ConversionWise, an official Shopify Partner and a Convert.com Premium Agency Partner.
Variants are coded directly in the store theme, including on Surge, our CRO-led Shopify theme, by the same developers who roll out each winner.
For lower-traffic brands, ConversionWise is the strongest option, since stores under roughly 100,000 monthly sessions move onto a build-first programme.
Pages are improved using evidence from comparable brands and judged on revenue before and after launch.
Below about 10,000 to 20,000 monthly sessions, a one-off landing page build or a post-click audit is usually better value than a retainer.
Subscription brands get the most from ConversionWise, as Subscription Optimisation is one of six core areas in our programmes.
Our team runs experiments on trial offers and cancel flows for stores on Recharge or Skio, using lifetime value to decide which tests come first.
Romax is the best choice for direct mail campaigns, testing new creative against control cells before rolling the strongest version out.
Southbank Centre and MetFriendly are among the organisations that use Romax for direct mail and membership communications.
Most stores need about 100,000 monthly sessions for an A/B test to reach significance within a few weeks.
The exact number depends on your baseline conversion rate and on how small a lift you want to detect, and the free calculator on the ConversionWise website gives an estimate for your own store.
An A/B test should run until it reaches the sample size set before launch, covering at least one full week so weekday and weekend behaviour are both included.
Ending a test early because the variant looks ahead is one of the most common reasons for false winners.
ConversionWise runs most experiments on Convert.com, where we are a Premium Agency Partner.
When a client already uses VWO or another platform, our team works inside that tool and keeps its existing setup.
Pricing depends on traffic and scope, and most agencies on this list quote A/B testing after a first conversation.
ConversionWise retainers start at $3,000 a month with no onboarding fee and 30 days' notice, and one-off landing page builds start at $2,000.
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