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What Is A/B Testing?
Conversion
Updated 18 September 2026
Quick Answer
A/B testing (or split testing) is comparing two versions of something — a headline, a button color, an email subject line — by showing each to a portion of your audience to see which performs better.
A/B Testing vs. Guessing — What's the Difference?
| A/B Testing | Guessing | |
|---|---|---|
| Basis for decision | Real visitor behavior | Opinion or assumption |
| Confidence | Measurable, repeatable | Unverified |
Why It Matters
- It replaces internal debate about which version is better with actual evidence from real visitors.
- Small, cheap tests (a headline, a button color) can meaningfully move conversion rate without a redesign.
How It Works
- Create two versions of one element, changing only that one thing.
- Show each version to a separate group of visitors at the same time.
- Measure which version performs better against a clear goal (clicks, sign-ups, sales).
Key Takeaways
- A/B testing compares two versions using real visitor behavior, not opinion.
- Change only one element at a time so you know what caused the difference.
- Start with high-impact, easy-to-change elements like headlines and CTAs.
Frequently Asked Questions
Do I need special software to run an A/B test?
Many email platforms and website builders have basic split-testing built in; dedicated tools exist for more advanced testing.
How long should a test run?
Long enough to get a meaningful amount of traffic to each version — a test stopped too early can show a misleading result.
What should I test first?
Start with something high-impact and easy to change, like a headline or a call-to-action button, rather than a minor design detail.