Why It Matters
Guessing what your subscribers want is expensive. A/B testing replaces gut feelings with real data, and even a small lift in open rate compounds over thousands of sends. Marketers who test regularly see 15-25% higher engagement within a few months because they're constantly tuning subject lines, send times, and layouts.
How It Works
You pick one variable to test — subject line, sender name, preview text, CTA button color, or send time. Your email platform splits a random sample (typically 10-20% of the list per variant) and delivers each version. After a set window (usually 2-4 hours), the platform checks which variant won on your chosen metric — opens, clicks, or conversions — and sends that version to everyone else.
The key rule: test only one variable at a time. If you change the subject line and the CTA, you won't know which change drove the result.
Quick Tips
- Start with subject lines — they have the biggest impact on open rates and they're the easiest to test.
- Wait at least 2 hours before picking a winner; shorter windows produce unreliable results.
- You need roughly 1,000+ recipients per variant for statistically meaningful results. Smaller lists can still test, but treat the data as directional.
- Log your test results somewhere. Patterns emerge after 8-10 tests that you'd never spot from a single send.