Most brands stick to what’s “safe”—but safe doesn’t scale. Without testing, you're likely leaving conversions, clicks, and subscribers on the table.

Klaviyo’s built-in split testing lets you experiment with flow timing, CTA phrasing, and more with minimal technical expertise. Many marketers focus primarily on subject lines, missing opportunities in flows and forms.

This guide gives you 12 proven A/B tests used by high-growth ecommerce brands to:

• Boost conversion rates in flows

• Increase campaign click-throughs

• Grow sign-ups with smarter form tests

Whether you’re a Klaviyo beginner or scaling retention across flows and SMS, these tests will help you make data-backed decisions that drive real revenue.

The Foundations of Klaviyo Split Testing

Split testing in Klaviyo helps brands optimise retention across email, flows, forms, and SMS by validating what drives performance—using real data.

Where You Can Split Test in Klaviyo

• Campaign Emails: Test subject lines, content, and design within the campaign builder. 

• Flows: Use the Random Sample split block to test different branches or timing strategies. 

• Sign-Up Forms: A/B test copy, visuals, offers, and triggers.

• SMS Campaigns: A/B testing isn’t supported natively; test by cloning messages and segmenting audiences, then track performance (e.g., click rate) in Klaviyo’s analytics.

How Klaviyo Handles Split Testing

• Split Logic: Default is 50/50, but flow tests allow custom splits (e.g., 70/30).

• Best Practice: Test one variable at a time for clean data

• Metrics Tracked: 

  • Campaigns: Open rate, click rate, revenue per recipient

  • Flows: Placed order rate, CTR, conversions per branch

• Audience Size: minimum of 5,000 recipients recommended for campaign tests

High-Impact Testing Areas

• Flows: Welcome Series, Abandoned Cart, Post-Purchase—these tend to have high traffic and clear conversion points

• Forms: Test pop-up timing, incentive type (e.g. % off vs. free shipping), and image vs. no image to lift submission rate

5 Campaign Email A/B Tests to Maximise Clicks & Revenue

Klaviyo campaign A/B tests go far beyond subject lines. You can test creative, layout, and CTAs to find what drives higher clicks and conversions.

What to Test in Campaign Emails

1. Subject Line

• Curiosity vs. clarity (“You’ll want to see this” vs. “Upgrade your order in 1 click”)

• Personalised vs. generic (“[First Name], here’s something better for you” vs. “Our premium pick is back”)

  
  

2. Preview Text

• Test urgency-focused lines (“Ends tonight”) vs. value-based lines (“Free delivery on all orders”)

3. CTA Placement

• Button at the top vs. bottom

• Text-only CTA vs. branded button

4. Image Hierarchy

• Full-width lifestyle imagery vs. cropped product close-ups

  
  

5. Tone & Layout

• Long-form storytelling vs. short punchy layouts

• Image-first vs. copy-first design

Best Practices for Running A/B Tests

• Minimum Audience: 5,000+ recipients for statistically significant results.

• Winning Metric: Define in advance—e.g. CTR or revenue per recipient.

• Smart Send Schedule: Set a customizable test window (e.g., 4 hours) in Klaviyo’s campaign builder, then the winning variant (based on your chosen KPI, like open rate or revenue per recipient) is sent to the remaining list.

• Test One Variable at a Time: Prevents false positives and reveals clear drivers of impact.

When NOT to A/B Test

• Audiences under 2,000 recipients (insufficient sample size)

• Flash sales or limited-time offers—where speed > learning

• Dependent variables (e.g. subject line + preview text) are being tested together

Pro Tip:

Klaviyo will automatically determine and send the winning variant to the rest of your audience—if you set up a test duration in the campaign builder.

4 Flow A/B Tests to Maximise Conversions

Klaviyo’s Random Sample feature in flows lets you A/B test automated journeys across key lifecycle stages.

Where to Use Flow Split Tests

1. Welcome Flow: Offer vs. No Offer

• What to Test: A 15% off first purchase incentive vs. no discount

• Goal: Maximise first-time purchase rate

• Why It Works: Some brands see stronger conversion without an offer when the brand story is strong.

For more strategic ideas, explore how to structure a high-converting Klaviyo Welcome Series that engages from first touch.

2. Abandoned Checkout: Plain Text vs. Image-Based SMS

• What to Test: Simple, text-only SMS vs. branded SMS with image and CTA

• Goal: Recover more carts via mobile

• Why It Works: Plain text can feel more personal, but visuals may improve urgency.

Learn how to set up, personalise, and optimise automations with our full breakdown of Klaviyo SMS Flows tailored for retention.

3. Post-Purchase Flow: Cross-Sell Product Logic

• What to Test: Personalised product recommendation vs. generic product block

• Goal: Increase repeat order rate

• Why It Works: Using dynamic blocks based on prior purchase (e.g., category or price tier) can improve conversions.

For a step-by-step strategy to increase AOV using tailored product blocks, read our full Klaviyo Cross Sell Flow guide—packed with logic types, examples, and visual templates.

4. Back-in-Stock Flow: Immediate vs. Delayed Send

• What to Test: Send alert instantly when back in stock vs. delay by 4 hours

• Goal: Balance urgency with timing sensitivity

• Why It Works: Delays reduce unsubscribes for customers who recently browsed but didn’t convert.

Need help automating urgency while staying subscriber-friendly? Our Back-in-Stock Email Guide breaks down trigger timing, copy ideas, and segment filters that convert.

How to Set Up a Flow Split Test

1. Add a Random Sample Split block at the desired point in your flow

2. Set variant percentages (e.g. 50/50 or 70/30 split)

3. Create unique paths for Variant A and Variant B

4. Track key performance metrics:

   • Click-through rate (Email or SMS)

   • Placed order rate

   • Revenue per recipient

Advanced Test Ideas

• SMS Timing: Send SMS before vs. after the email

• Product Blocks: Dynamic recommendations vs. static banners

• Email Format: Plain text vs. HTML design

Pro Tip: Always test one variable at a time. This ensures you know exactly what’s driving the results.

3 Signup Form A/B Tests to Boost Sign-Up Rate

Signup forms are your frontline for list growth—but even small tweaks can mean big differences in performance. Klaviyo lets you A/B test key elements of your forms to uncover what drives higher engagement and conversions.

1. Headline: Benefit-Led vs. Curiosity-Led

• Test Example:

  • Benefit-led: “Get 10% Off Your First Order”

  • Curiosity-led: “Unlock a Surprise Offer”

    
    

• Why It Works:
  Headlines are the first thing users read. Benefit-led headlines are clear and direct, while curiosity-led headlines can drive intrigue and clicks.

• KPI: Form submission rate

• Insight: Brands with high traffic often find that direct benefit-led headlines outperform on desktop, while curiosity-led variations convert better on mobile.

2. Offer Type: % Discount vs. Free Shipping

• Test Example:

  • 10% Off vs. Free Shipping on First Order

    
    

• Why It Works:
  Some customers are more price-sensitive, while others react more to convenience. The right offer depends on your AOV and shipping costs.

• KPI: Submission rate, revenue per subscriber

• Insight: Klaviyo data suggests free shipping often performs better for lower AOV products, while % discounts work best for higher-ticket items.

3. Trigger Timing: Scroll Trigger vs. Exit-Intent

• Test Example:

  • Show form after 50% scroll vs. when user tries to exit

• Why It Works:
  Timing matters. Scroll-based triggers engage actively browsing users, while exit-intent captures those about to bounce.

• KPI: Submission rate, bounce rate impact

• Insight: For returning visitors, scroll triggers tend to convert better; for first-timers, exit-intent captures more leads.

Signup Form A/B Test Ideas by Visitor Type

If you’re designing or improving your opt-ins, don’t miss our full Klaviyo Sign-Up Forms guide for UX, A/B tests, and mobile best practices.

Use Holdout Groups to Measure True Lift

Holdout groups enable you to measure the true impact of automation by excluding a portion of your audience and comparing the results. This shows whether your flow adds incremental value beyond natural behaviour.

When to Use Holdouts

Ideal for high-impact automations like:

• Welcome Series – Measure the impact of nurturing on first-time purchases.

• Post-Purchase Flows – Track the impact of cross-sell or educational efforts on reorders.

• Loyalty/Referral Campaigns – Test if emails boost programme participation.

• Win-Back Automations – Compare re-engagement vs. passive return rates.

Best Practices

• Holdout Size: 10–20% of eligible users.

• Run Time: Minimum 30 days or until statistically valid.

• Metrics: Focus on placed order rate, revenue per recipient, and LTV.

How to Set It Up:

1. Add a Random Sample split at the start of your flow.

2. Send 80–90% through the full automation; direct 10–20% to a no-message path.

3. Tag or segment both groups for reporting.

Reading the Results

• If the active group has a 14% order rate vs. 9% in holdout, the flow yields a 5% lift.

• Analyse LTV differences using cohort reporting or tools like Lifetimely.

• No lift? Reassess your content, cadence, or targeting before scaling.

Build a Strategic Split Testing Roadmap

A solid A/B testing strategy should align with your customer journey and business goals. Testing blindly wastes time—map tests to funnel stages and prioritise by impact.

Test Ideas by Funnel Stage

How to Prioritise Testing

• Start with high-volume flows (Welcome, Cart, Post-Purchase).

• Focus on impact: Revenue-driving steps > cosmetic tweaks.

• Use a calendar to plan 1–2 split tests per month.

• Avoid testing too many variables at once or over-testing small segments.

Build Your Testing Calendar

• Plan by theme (e.g. CTA, subject line, send time).

• Document goals, metrics, and learnings in a shared log.

• Rotate test types across email, SMS, and form touchpoints.

Analyse Results and Scale What Works

Running A/B tests is only half the job—interpreting results correctly is where the real value lies. Klaviyo provides built-in reporting, but it's your job to translate insights into action.

Key Metrics to Monitor

• Open Rate (for subject line tests in email only)

• Click-Through Rate (CTR)

• Revenue Per Recipient (RPR)

• Order Rate (conversion-focused tests)

• SMS Click Rate (for SMS variant tests)

For more ideas on driving engagement, explore our Klaviyo Click-Through Rate guide covering copy, layout, and optimisation strategies.

What to Do After a Test Ends

• Promote the winning variant to default.

• Launch a follow-up test with a new variable.

• Document results in a shared testing log to build learnings over time.

Create a Feedback Loop

• Include top-performing test results in your campaign briefing.

• Share wins with design, copy, and product teams to reinforce best practices.

• Use Klaviyo's profile filters or tags to pause or isolate underperforming versions quickly.

Avoid Common Split Testing Mistakes

Even well-structured A/B tests can fail if set up or misinterpreted. These common mistakes can lead to false positives, wasted resources, or misleading results.

Common Split Testing Mistakes (and How to Fix Them)

FAQs

1. Can I run more than one A/B test at a time in Klaviyo?

• Yes, but keep tests separate by flow, campaign, or form to avoid overlapping variables that could skew your results.

2. How do I know if my test is statistically significant?

• Klaviyo provides confidence levels once a sample size threshold is met. For small lists, extend test duration or lower your significance goal slightly.

3. Does split testing affect my deliverability?

• No, unless you're sending high-volume tests with major content shifts. Keep subject lines and tone aligned with your usual brand voice.

4. Can I automate follow-up based on test winners?

• Yes. In flows, you can route users based on winning paths. For campaigns, Klaviyo automatically sends the winning variant after the test period ends (if selected).

5. Should I test for mobile and desktop audiences separately?

• It's a good idea. Use Klaviyo's segmentation to split test by device type if you suspect UX or messaging performs differently by platform.

Conclusion

Feeling stuck with flat email results or slow subscriber growth? You're not alone. Many brands plateau because they repeat what’s worked before—without testing what could work better. Klaviyo’s split testing tools aren’t just for subject lines; they’re a powerful way to uncover what really moves the needle across your flows, campaigns, and forms. 

This guide gave you 12 proven tests used by top-performing ecommerce brands to boost engagement and revenue. So don’t guess—experiment. Small changes, tested smartly, can lead to big breakthroughs. The next conversion surge might be just one A/B test away.

Key Takeaways

• Go Beyond Subject Lines: Most brands underuse Klaviyo's testing tools—flows and forms offer bigger impact.

• Use Flow Split Logic: Test timing, tone, and CTA style to improve LTV and post-purchase engagement.

• Form Tests Drive Growth: Pop-up copy, incentives, and trigger timing can double your list sign-ups.

• Track the Right Metrics: Focus on conversion rate and revenue per recipient—not just open rate.

• Document & Repeat Winners: Keep a log of what works and apply those learnings across channels.

• Test One Variable at a Time: To learn what really works, isolate changes and wait for valid results.

Overwhelmed by split testing options in Klaviyo?

Whether it’s SMS, email, forms, or flows—we’ll identify what to test, how to test it, and how to scale what succeeds. Click here to get a free expert audit and eliminate the guesswork.