Key Takeaways
- A/B testing compares two versions to see which performs better, but only a disciplined test gives a real answer.
- Test one meaningful change at a time, or you won't know what moved the result.
- Most tests fail because the sample is too small or the test is called too early.
- Test things that matter, subject lines, offers, headlines, not button colors.
- Measure the metric tied to your goal, and act only on differences that are real.
What Is A/B Testing and Why It Matters
A/B testing means showing two versions of an email or landing page to comparable audiences, then keeping the one that performs better on a metric you choose. It's how you replace guesswork with evidence, steadily improving open rates, click rates, and conversions instead of arguing about opinions.
The catch is that most tests teach nothing, because they change several things at once, run on too few people, or get called the moment one version edges ahead. Done with discipline, a test gives you a true, repeatable lesson. Done carelessly, it produces confident conclusions from pure noise. The method matters more than the tool.
How to Set Up an A/B Test: Step-by-Step
A/B testing options depend on your Marketing Hub tier, so confirm what's available in your portal before you start.
Step 1: Pick One Thing to Test
Choose a single, meaningful variable and form a clear hypothesis about why B might beat A. Good things to test:
- The email subject line.
- The landing page headline
- The offer or call to action
- The send time or form length
Step 2: Create the A/B Version
- Open the email or landing page in the editor.
- Create an A/B test from the editor options.
- Build version B changing only the one element you chose.
- In HubSpot, A/B testing is built into the email and page editors; confirm the exact option in your tier.
Step 3: Set the Split and Sample
- Decide how traffic or recipients split between versions A and B.
- Make sure the audience is large enough for the result to mean something.
- Be honest if your list is too small to test reliably.
- For small lists, test bigger swings or gather more data first.
Step 4: Define the Winning Metric Up Front
Choose the metric that matches your goal before you start, so you don't move the goalposts later:
- Open rate for subject line tests.
- Click rate for content and CTA tests.
- Conversion rate for landing page and offer tests.
- Pick one primary metric, not several.
Step 5: Run, Then Read Honestly
- Let the test run to enough volume and over enough time.
- Check whether the difference is meaningful or could be chance.
- Act on the winner only if the gap is real.
- If it's a near-tie, treat it as no clear winner, not a result to chase.
Best Practices for A/B Testing
- Test One Variable at a Time: If version B changes several elements and wins, you won't know which change did it. Isolate a single variable so the lesson is clear.
- Test Things That Matter: Put effort into subject lines, headlines, and offers, the elements that move results. Cosmetic tweaks rarely pay off.
- Give the Test Enough Volume: A few hundred contacts produces noise, not signal. Run on a large enough audience for the result to be real.
- Let It Run Long Enough: An early lead on day one often vanishes. Wait for enough data and time before calling a winner.
- Act Only on Real Differences: Treat a result as a finding only when the difference is meaningful, not when one version squeaks ahead by chance.
How to Use A/B Testing in Your Workflow
- Test subject lines on every major email send to steadily lift open rates
- A/B test landing page headlines and offers before driving paid traffic to them
- Document each result so findings compound instead of being forgotten
- Feed the winning version into your templates so improvements carry forward
Troubleshooting Common A/B Testing Issues
Problem: The winner performs no better when rolled out
Solution: You likely called it too early or on too small a sample. The original gap was noise. Wait for volume and a meaningful difference.
Problem: You can't tell what caused the win
Solution: Version B changed more than one thing. Re-run the test changing only a single element so the result is attributable.
Problem: Tests never produce a clear winner
Solution: Your list may be too small, or you're testing trivial elements. Test bigger, higher-impact changes and gather enough data.
The Bottom Line
A/B testing is one of the most reliable ways to improve marketing results, and one of the easiest to do badly. Test one meaningful thing at a time, run on enough people, and act only on differences that are real, and each result becomes a true lesson you can build on. Test carelessly and you're just making confident decisions from randomness.
The Markivis Approach
We test with discipline, so every result is a lesson you can trust:
- Isolate one variable: We change a single meaningful element per test, so we know exactly what moved the result.
- Test what matters: We put effort into subject lines, offers, and headlines, not cosmetic tweaks that rarely pay off.
- Wait for real volume: We run tests on a large enough audience and long enough, so an early lead doesn't get mistaken for a finding.
- Document every result: We record what won and why, so improvements compound instead of getting forgotten.
This disciplined, test-and-learn approach is how we strengthened Beyond Codes' employer brand to attract over 1,200 top-talent applications, improving what worked and dropping what didn't based on real evidence. See the Beyond Codes case study.