A/B testing (also called split testing) is the process of sending two different versions of an email to small segments of your list, measuring which performs better, and sending the winning version to your remaining subscribers. It’s the scientific method applied to email marketing — and it’s one of the most reliable ways to consistently improve your results.
Why A/B Testing Matters
Without testing, email marketing decisions are based on gut feeling and assumption. With consistent A/B testing, you build a library of data-driven insights specific to your audience. You learn what subject lines they respond to, what offers convert, what CTAs they click, and what content they find most valuable.
Compounded over time, these marginal improvements produce dramatically better email performance.
What to A/B Test
You can test almost any element of an email, but the highest-impact variables to start with are:
Subject LineThe most common and highest-impact A/B test. Even a 5% improvement in open rate across 10,000 subscribers means 500 additional people reading your email.
Send TimeDoes your audience open more emails at 7 AM or 12 PM? On Tuesday or Thursday? Test systematically across different days and times over several months.
Preview TextThe preview text (also called the preheader) appears below the subject line in most email clients. A compelling preview text can lift open rates significantly.
CTA Button vs. Text LinkDoes a prominent button drive more clicks, or do readers respond better to a simple hyperlinked text call to action?
Email LengthDo your subscribers prefer concise, punchy emails or longer, more detailed ones? Test 200-word emails against 600-word emails to the same segment.
PersonalizationEmails addressing the subscriber by first name in the subject line vs. not. This often improves open rates by 10–20%.
Offer TypeDoes a percentage discount (20% off) outperform a flat dollar discount ($20 off)? Does free shipping beat a price reduction?
Image vs. No ImagePlain-text emails often outperform heavily designed ones for certain audiences and email types. Test both.
How to Run a Proper A/B Test
Test only one variable at a time. If you change both the subject line and the email length, you won’t know which variable drove the difference.
Use a statistically meaningful sample size. Most email platforms need at least 1,000 recipients per variation for reliable results.
Define success before you test. Is the winning metric open rate, click rate, or conversion rate?
Let the test run long enough to collect meaningful data (typically 4–6 hours for time-sensitive tests like subject lines).
Document your results. Build a testing log that records what you tested, which version won, and by how much. This library becomes increasingly valuable over time.
Readers may also want to visit US-creditcards.com.
UK A/B Testing Insights
UK audience preferences in email can differ from US audiences. British readers often respond differently to humor, directness, and urgency tactics. Your A/B testing data will reveal what works specifically for your UK subscribers over time. You can also visit economicsandmoney.com for more reading.
A/B Testing and Business Value
A business with documented A/B testing history and improving email benchmarks demonstrates marketing sophistication and growth trajectory. For a related read on this site, see How to Measure the ROI of Your Content.
Test methodically, document everything, and let the data drive your email strategy.
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