What is an A/B split test in email marketing?
An A/B split test involves sending two versions of an email to two segments of your audience. The goal is to find out which version performs best. The winner is then sent to the rest of your list.
It is a simple yet powerful method for improving open rates, click rates and conversions in your email marketing.
What can you test?
There are many options for A/B testing in email marketing. Here are some of the most commonly used:
- Subject lines: Test short vs. long, with/without emojis, personalised elements.
- Sender name: Brand name alone or combined with a person's name.
- Design and layout: Plain text email vs. graphic template.
- Call-to-action (CTA): Button colours, placement and wording.
- Content length: Short and concise vs. long and explanatory.
- Offer types: Percentage discount vs. free shipping.
- Send times: Morning, midday or evening.
How do you ensure valid results?
To get value from your tests, it is important to follow some basic principles:
- Test only one variable at a time – otherwise you won't know what caused the difference.
- Ensure a sufficiently large audience – otherwise the results will not be statistically valid.
- Use a clear KPI focus – do you want to optimise opens, clicks or sales?
- Repeat tests on an ongoing basis – consumer behaviour changes over time.
When does it make sense to A/B test?
It makes the most sense when you have:
- A larger mailing list, where you can split into test groups without losing reach.
- Campaigns where even small improvements can have a significant impact on the bottom line.
- Hypotheses you want to validate, rather than simply “shooting in the dark”.
Example
A brand tested two different subject lines on a campaign email:
- Version A: “Save 20% this weekend”
- Version B: “For 48 hours only: 20% off”
The results showed that version B achieved a 12% higher open rate. By scaling the winner to the entire list, they generated a noticeably higher revenue from the campaign.
Conclusion
A/B split testing is one of the most valuable tools in email marketing. It requires a systematic approach, but can quickly deliver insights that directly improve performance.
By testing everything from subject lines to call-to-actions, you can learn what works best for your specific audience – and use that knowledge to drive continuous growth.
