Your online store is like a really long checkout line. People can (and will) get impatient, frustrated, and confused and leave. If that happens, you’re losing sales before they even get to the counter. Conversion rate optimization helps clear the path so more shoppers actually finish their purchase.

Studies show that even a one-point lift in conversion rates can translate into millions in added revenue for eCommerce businesses. Small gains matter a lot in a competitive market, where most players have huge budgets for traffic acquisition.

And while you could try to run a testing program yourself, most in-house teams lack the bandwidth, tooling, or structured methodology to get consistent results. Partnering with a specialized CRO agency brings proven frameworks, case study experience, and the focus needed to turn testing into real revenue.

How We Selected the Top Agencies

We focused exclusively on CRO agencies with a proven track record in eCommerce. Our criteria emphasized measurable client results, vertical expertise, pricing transparency, and cultural fit.

To ensure rigor, we cross checked against well known industry resources such as CXL’s experimentation reports, VWO and Optimizely case study libraries, and reputable roundups in outlets like Practical Ecommerce. We also excluded well known names you specifically wanted left out, ensuring this list brings some fresh but credible players to the table.

Ranking Criteria We Used

Before diving into the list, it helps to know how we judged the contenders. Think of these criteria as the yardsticks we used to separate hype from hard proof. Each factor matters for different reasons, from ROI to culture fit.

• Proven performance: Case studies, public metrics, or revenue lift figures that show they deliver results. If there’s a guarantee, we award it more points.
• Industry expertise: Specialization in eCommerce and DTC brands, not just generic marketing. No companies where CRO are just an afterthought.
• Pricing models: Clarity on whether they charge performance based, retainer, or project fees.
• Fit and communication: team bandwidth, transparency, and cultural alignment that makes collaboration work

Data Sources & Methodology

We drew from public case studies, client testimonials, and industry roundups. We also included each agency’s own published results.

Where available, we cite client outcomes to give you a real sense of what each firm can deliver.

TL;DR Comparison Table

If you’re in a hurry, here’s the summary version. This table gives you the highlights at a glance before we dive into each agency’s full profile.

Rank	Agency	Typical Wins	Best For	Standout Proof	Pricing
1	Spiralyze	30% lift in 90 days	Mid to large eCommerce brands	Proprietary prediction engine, performance guarantee	Performance based
2	Speero	Systematic testing at scale	DTC and complex commerce	Work with Dr. Squatch, experimentation programs	Retainer/project
3	SplitBase	Multi million revenue lifts	Premium DTC and luxury	Landing page/PDP optimization for high end brands	Retainer
4	The Good	$100M+ incremental revenue	Established eCommerce	Decade long track record, case study library	Retainer
5	Oddit	Quick design wins	Fast moving DTC brands	Client quotes about beating controls	Flat fee audits
6	Outerbox	Documented add to cart lifts	Longstanding online retailers	VWO case studies, industry leadership	Retainer

1. Spiralyze: CRO with a Performance Guarantee

Spiralyze makes bold promises, and backs them up. They guarantee at least a 30% conversion lift in 90 days, or you don’t pay.

Their edge is a proprietary prediction engine trained on data harvested from more than 78,000 websites that actively A/B test, capturing over 8,000 new tests every month. This depth of data lets them move faster and smarter than most agencies.

On top of that, Spiralyze operates as a full service partner, handling design, development, analytics, and testing under one roof.

Spiralyze is a great CRO for eCommerce, B2B and SaaS companies.

Main Services:

• A/B and multivariate testing
• Landing page and funnel optimization
• Full stack CRO program design

Prominent Clients and Results:

• ADT Security: landing page redesign tests produced conversion lifts of 40–90%
• Kaplan: achieved consistent improvements on lead generation funnels
• AutoNation: multiple campaigns with over 30% conversion rate increases

2. Speero: Experimentation at Scale

Speero, spun out of the CXL ecosystem, is known for building experimentation programs that stick. Their work with brands like Dr. Squatch shows how they help eCommerce companies not just test pages, but systematize experimentation into the business.

They’re best for ambitious DTC companies that want testing to become a growth engine rather than a side project.

Main Services:

• Experimentation program management
• User research and customer journey mapping
• Data analysis and test design

Prominent Clients and Results:

• Dr. Squatch: scaled testing program into a structured growth engine
• Procter & Gamble: generated $1.5M in additional revenue through CRO improvements
• MongoDB: went from zero experiments to 100+ per year in under six months

3. SplitBase: CRO for Luxury and Premium DTC

SplitBase is the go to for brands that want persuasion heavy landing pages and optimized product detail pages. They’ve helped premium DTC brands generate multi million dollar lifts by refining storytelling and nudging users through high value buying journeys.

If you’re selling prestige products, they understand the psychology of that buyer.

Main Services:

• Landing page optimization
• Product detail page optimization
• Copywriting and UX research

Prominent Clients:

• L’Oréal
• Kiehl’s
• Four Sigmatic

4. The Good: Proven CRO Veterans

The Good has been optimizing eCommerce sites for over a decade. Their case study library points to hundreds of millions in added revenue.

They combine research, testing, and UX to help established brands unlock sustained growth. Their reputation and published results make them one of the safest bets in the CRO space.

Main Services:

• Conversion audit and testing programs
• UX and usability research
• Personalization strategy

Prominent Clients:

• Nike
• Adobe
• Xerox

5. Oddit: Fast Audits, Fast Wins

Oddit takes a different tack: sharp design first audits that produce quick, impactful fixes. Their landing page redesigns are often cited by clients as outperforming long standing control versions.

They’re ideal for fast moving DTC brands that need wins yesterday, not six months down the line.

Main Services:

• Landing page audits
• CRO design makeovers
• UX/UI recommendations

Prominent Clients:

• Chamberlain Coffee
• Caraway
• Haus

6. Outerbox: Testing Veterans with Staying Power

Outerbox has been in the optimization game for years. They have documented add to cart lifts published through partners like VWO.

Their experience spans large catalogs and complex eCommerce systems. This makes them a fit for retailers that need a seasoned partner. They also contribute heavily to CRO education, underscoring their thought leadership role.

Main Services:

• A/B testing and personalization
• Analytics implementation and insights
• UX and site performance optimization

Prominent Clients:

• The Vitamin Shoppe
• Godiva
• TaylorMade Golf

How to Pick the Right CRO Partner

Picking a CRO agency is a bit like choosing a gym trainer. The best one isn’t the biggest name, it’s the one who fits your style, goals, and pace.

Here are a few fresh angles to weigh:

• Experimentation philosophy: Do they believe in high volume rapid tests or carefully crafted fewer tests? Match their approach to your tolerance for risk and speed.
• Creative vs. data balance: Some agencies lean into bold design overhauls, others focus on incremental, evidence led tweaks. Which mix feels right for your brand?
• Learning culture: Great CRO partners don’t just run tests, they transfer knowledge to your team. Look for agencies that document, teach, and leave you smarter.
• Industry empathy: Beyond “we know eCommerce,” do they understand the quirks of your vertical, whether that’s fashion, luxury, or subscription boxes?

Futureproofing: Ask how they handle shifting privacy laws, GA4 tracking changes, and evolving user behavior.