Email Marketing A/B Testing: A Beginner's Guide

You may have two subject lines, two calls to action, or two different versions of an email and wonder which one your subscribers will respond to. Instead of relying only on assumptions, email marketing A/B testing lets you compare versions with a selected audience and learn from actual campaign results.

What Is Email Marketing A/B Testing?

Email marketing A/B testing, also called split testing, is a method of comparing two versions of an email or a specific email element.

For example, a marketer might create two different subject lines while keeping the rest of the email the same. One group of subscribers receives Version A, while another group receives Version B.

The marketer then compares an appropriate performance metric to determine whether one version produced a better result.

The main purpose is to learn from actual subscriber behavior rather than relying only on personal opinions or assumptions.

Why Is A/B Testing Important?

Different audiences can respond differently to email content. An element that works well for one audience may not produce the same result for another.

A/B testing can help marketers:

• Make decisions based on campaign data
• Understand subscriber preferences
• Improve email engagement
• Improve click activity
• Identify stronger messaging
• Improve future campaigns
• Reduce guesswork

A/B testing works especially well when it becomes part of an ongoing improvement process rather than a one-time experiment.

How Does Email A/B Testing Work?

A basic A/B test follows a simple process.

1. Choose one element to test.
2. Create Version A.
3. Create Version B.
4. Define the audience or test groups.
5. Choose the main metric.
6. Send the test.
7. Collect enough results for a useful comparison.
8. Evaluate the results.
9. Apply the learning to future campaigns.

The exact testing features available will depend on the email marketing platform being used.

What Can You A/B Test in Email Marketing?

Many different email elements can be tested. Common examples include:

How to A/B Test Subject Lines

Subject lines are one of the most common elements to test because they appear before a subscriber opens an email.

When testing subject lines, keep the rest of the email as consistent as possible so that the test provides a clearer comparison.

How to A/B Test Preview Text

Preview text provides additional context alongside the subject line in many email clients.

Marketers can test different preview messages to see whether a particular combination creates stronger engagement.

For example:

• Version A: Learn the basics in five practical steps.
• Version B: Start improving your campaigns today.

How to A/B Test Email Content

Email content can be tested in several ways. A marketer might compare a shorter message with a more detailed explanation, or test two different ways of presenting the same offer.

When testing content, it is useful to change one major variable at a time. Otherwise, it can become difficult to determine what caused the difference.

Good email copy should also be clear and relevant to the audience. See What Is Email Marketing Copywriting? for more information.

How to A/B Test Calls to Action

A call to action, or CTA, tells the subscriber what action to take.

For example, you could test:

• Learn More
• Read the Full Guide

Or you might compare a product-focused CTA with an educational CTA depending on the purpose of the email.

How to A/B Test Images

Images can also be tested when visual content plays an important role in an email.

Possible tests include:

• Product image vs. lifestyle image
• One image vs. multiple images
• Image-heavy design vs. text-focused design
• Different image placements

The test should have a clear purpose. Changing images without measuring a relevant outcome does not provide much useful information.

How to A/B Test Email Sending Time

Sending time can be tested when a business wants to understand whether different delivery times produce different engagement.

For example, a business might compare a morning send with an afternoon send. However, the best time can vary depending on the audience, location, business type, and purpose of the email.

Testing is therefore more reliable than assuming that one universal sending time works for every audience.

How to Run an Email A/B Test Step by Step

Step 1: Define the goal

Decide what you want to learn. Your goal might be to improve clicks, engagement, conversions, or another relevant outcome.

Step 2: Choose one variable

Select one main element to test, such as the subject line or CTA.

Step 3: Create two versions

Create Version A and Version B. Keep other important elements as similar as possible when you want to isolate the effect of the variable being tested.

Step 4: Define the test audience

Decide which subscribers will participate in the test. Your email platform may provide specific options for creating test groups.

Step 5: Select the main metric

Choose the metric that best matches the purpose of the test.

Step 6: Run the test

Send both versions according to your testing plan.

Step 7: Evaluate the results

Compare the results rather than choosing a winner based on a small or isolated difference without considering the quality of the data.

Step 8: Record what you learned

Document the test, result, audience, variable, and main learning. This creates a useful knowledge base for future campaigns.

Step 9: Apply the learning

Use the result to inform future emails, while remembering that a result from one audience or campaign may not automatically apply to every future campaign.

Email A/B Testing Example

Which Email Metrics Should You Measure?

The right metric depends on what you are testing.

A single metric should not always be treated as the complete picture. For example, a version that generates more opens may not necessarily generate more meaningful actions after the email is opened.

Common Email A/B Testing Mistakes

Mistake 1: Testing too many variables at once

If you change the subject line, content, CTA, image, and sending time at the same time, it can be difficult to identify which change caused the result.

Mistake 2: Testing without a clear goal

Every useful test should answer a meaningful question.

Mistake 3: Choosing a winner too quickly

Very early results may not provide enough information for a reliable conclusion. Follow the testing guidance and capabilities of your email marketing platform.

Mistake 4: Ignoring the audience

A test result can depend on the audience receiving the message. A result from one segment may not automatically apply to another.

Mistake 5: Focusing only on open rates

Opens can be useful in some contexts, but clicks, conversions, revenue, and other outcomes may be more important depending on the campaign goal.

Mistake 6: Running tests without recording results

If you do not document what was tested and what happened, you may lose valuable lessons for future campaigns.

Email A/B Testing Best Practices

• Start with a clear question.
• Test one major variable at a time when possible.
• Choose a metric that matches the test goal.
• Keep test conditions consistent.
• Use an appropriate audience.
• Allow enough time for meaningful results.
• Document every important test.
• Use results as evidence rather than assuming they apply everywhere.
• Repeat useful tests when appropriate.
• Use testing as part of continuous improvement.

Email Marketing A/B Testing Checklist

Frequently Asked Questions

What is A/B testing in email marketing?

A/B testing in email marketing is the process of comparing two versions of an email or email element to determine which performs better according to a chosen metric.

What is an example of email A/B testing?

A simple example is sending two different subject lines to comparable test groups and comparing their results to determine which subject line performs better under the test conditions.

What should I A/B test first in email marketing?

Subject lines are a common starting point, but the best first test depends on your campaign goal and where you see the greatest opportunity for improvement.

How many things should I test at once?

For a straightforward A/B test, testing one major variable at a time makes it easier to understand what caused the difference between the two versions.

How long should an email A/B test run?

There is no single duration that works for every campaign. The appropriate period depends on factors such as audience size, sending frequency, campaign type, and the testing capabilities of your email platform.

Is A/B testing useful for small email lists?

A/B testing can still provide learning opportunities with smaller lists, but smaller audiences may produce less reliable or less conclusive differences. Interpret results carefully.

Can I A/B test automated emails?

Some email marketing platforms provide testing features for automated messages. Whether and how you can test an automated email depends on the platform and the type of automation.

Learn more about automated email campaigns in What Is Email Marketing Automation? .

Does A/B testing guarantee better email performance?

No. A/B testing is a learning method, not a guarantee of improvement. Some tests may produce little difference, while others may reveal a useful improvement.

Conclusion

Email marketing A/B testing gives marketers a structured way to learn what works better for their audience. Instead of changing campaigns based only on assumptions, marketers can compare versions and use measurable results to guide future decisions.

Start with a clear goal, test one important variable, choose an appropriate metric, evaluate the results carefully, and document what you learn.

Over time, consistent testing can become an important part of an email marketing strategy and help businesses continuously improve their campaigns.