The Ultimate Guide to Email A/B Split Testing | AWeber (2023)

By Kaleigh Moore May 16, 2023

In a world where people are bombarded with countless emails on a regular basis, it’s more important than ever to craft emails with purpose.

In 2022, over 333 billion emails were sent and that figure is expected to rise to a staggering 376 billion by 2025.

The Ultimate Guide to Email A/B Split Testing | AWeber (1)

These days it’s not enough to assume you know what type of email your audience will want to open — let alone read through it entirely.

Creating great emails requires a lot of hard work, researching, and strategizing. The best emails are crafted not only with goals in mind, but also with the target audience at the forefront.

So how can you be sure which email will be more successful than others?

You’re not the first person to ask that question.

What if there was a way to be sure that one version of an email would generate more engagement, lead to more landing page views, and/or provoke more sign ups?

Well . . . there is – with testing.

Testing your emails is a brilliant way to determine what resonates with your audience and what sparks their interest. With email A/B testing, you can gather data-backed proof of the effectiveness of your email marketing.

In this guide to email A/B testing you’ll learn

  • What is A/B testing
  • Why you need to split test your emails
  • Setting goals for A/B testing
  • What you should test
  • Email A/B test case study
  • Best practices for email testing
  • Setting up an A/B email test
  • Tracking and measuring A/B test results
  • Get started with your own email test

And by the end you’ll know how to set up a successful email split test.

But before we get started, it’s important to know what email marketing A/B split testing is.

What is A/B testing?

A/B testing, also known as split testing, is a method that lets you scientifically test the effectiveness of an experiment, in this case, an email experiment.

When split testing, you create two versions (called variants) of an email to determine which email statistically performs better. Once you find which email variant performs best, you can update your email strategy based on what you learned about the winning email.

This allows you to identify what emails engage your subscribers best, which can ultimately help you increase conversions and revenue.

Why you need to split test your emails

Split testing is an effective way to find out what’s working and what’s not in your email marketing. Rather than assuming your customers would prefer one kind of email over another, you can run a split test to find out in a methodical way.

The more you split test, the more information you’ll have on hand for your future emails. And while a once-and-done test, or even an occasional test, can yield information that will expand your marketing knowledge, regular testing can provide you with a long-term successful email marketing strategy.

(Video) A/B split testing in email builder

Setting goals for A/B testing

Like anything in digital marketing, having a clear goal and purpose for testing is essential. Sure, you can run a quick email test and obtain useful results, but having a more precise testing strategy will yield more powerful data.

A/B testing your emails is a great tool to use at any time, but it can be especially useful if you want to gain insight on a new campaign or email format. Before you begin your test, first establish what you are testing and why.

A few questions that can help guide you at this stage include:

  • Why are we testing this variable?
  • What are we hoping to learn from this?
  • What is the impact this variable has in relation to the performance of this email?

In theory, you could test any element of an email, but some variables will give you more insight into your subscribers’ minds than others.

The beauty of split testing is that no variable is too small to test.

What you should test

It can be tricky to identify what test can help you improve key metrics. From subject line strategies to sound design principles, there are many components that make up a successful email. Understanding each email key performance indicator (KPI) and the email components that impact those KPI’s helps identify what you should be testing.

Open rate

Your open rate is the percentage of customers who opened your email. It’s calculated by dividing the number of unique opens by the number of emails delivered.

The Ultimate Guide to Email A/B Split Testing | AWeber (2)

If you have a low open rate you should be testing your subject line or preheader (the preview snippet of text that is next to your subject line or below it (on mobile) in your inbox).

Subject lines are crucial because they’re the first things people see in their inbox. Split testing your subject lines can help make for more successful emails.

Subject line test ideas:

  • Short vs long subject line
  • More urgent language
  • Try an emoji
  • All capitalized words vs sentence case
  • With and without punctuation marks
  • Single word subject lines
  • Statement vs question

The better your subject line, the more likely your subscribers are to open the email and read through. Having a solid subject line is like getting your foot in the door.

In addition to testing subject lines, try sending the test emails at different times of day and see if that has an impact on your open rate. Your subscribers may be more inclined to open an email in the morning or at night after dinner instead of during the middle of a workday.


The Ultimate Guide to Email A/B Split Testing | AWeber (3)

Click-through to open rate

Your click through to open rate is the percentage of unique clicks in an email divided by the number of unique opens.

The Ultimate Guide to Email A/B Split Testing | AWeber (4)

There are several elements within the body of your email which you need to look at if you have a low click through to open rate or if you’re looking to improve an already strong email.

The Ultimate Guide to Email A/B Split Testing | AWeber (5)

Keep subscribers interested throughout the email by providing eye-catching, engaging content. If it’s your click-through rate you want to improve, make sure you create clickable content. Consider how interactive content, information gaps (missing pieces of info that spark a reader’s curiosity), or contests could boost your in-email engagement.

There are also many variables you can test to optimize for click-through rate — a strong call to action, intriguing anchor text, personalization, spacing, or bold imagery. Just remember to test one at a time to ensure you know precisely why subscribers are clicking more (or less).

This is why testing is so important. You can look at an email and make some assumptions as to why your performance is low. But if a change is made without testing and that theory is wrong, then you’re setting your email efforts back even further.

Email body test ideas:

  • Different color call to action button
  • Image vs no image
  • Email message length
  • Soft sell vs hard sell
  • GIF vs no GIF
  • Personalization vs no personalization

Design elements like colors, fonts, images, templates, and spacing are just as crucial to an email as the copy and links.

Did you know that 47% of emails are opened on mobile devices? With this in mind, think about how your email visually appeals to subscribers and what they need to get the best reading experience.

(Video) How to quickly and easily A/B test your emails

Test different templates, layouts, and formats to see which yields the best results for your email campaigns.


The Ultimate Guide to Email A/B Split Testing | AWeber (6)
The Ultimate Guide to Email A/B Split Testing | AWeber (7)
The Ultimate Guide to Email A/B Split Testing | AWeber (8)
The Ultimate Guide to Email A/B Split Testing | AWeber (9)
The Ultimate Guide to Email A/B Split Testing | AWeber (10)

Opt-out (or unsubscribe) rate

Your unsubscribe rate is the percentage of customers who opt-out of receiving future emails from you.

The Ultimate Guide to Email A/B Split Testing | AWeber (11)

If your unsubscribe rate is high, then you may be sending too many emails or the email content isn’t relevant.

So make sure you test the frequency of emails and the relevancy as discussed above.

Email A/B test case study

AWeber customer and photo sharing community Light Stalking split their email subject lines to gauge the success of one versus the other.

The Ultimate Guide to Email A/B Split Testing | AWeber (12)
The Ultimate Guide to Email A/B Split Testing | AWeber (13)

As a result, they were able to increase their web traffic from the winning subject line email by 83%.

How’d they do it?

Light Stalking wanted to run an email A/B test on the subject line of their weekly challenge email, which asked subscribers to send in a photo of a silhouette.

The test was simple: they created two identical versions of the same email, changing only the subject lines. The first email used a straightforward subject line, “The Weekly Challenge is Live!” and the second email was just one word and hinted at the nature of the challenge, “Silhouettes.”

The email with the shorter headline (“Silhouettes”) was the winner. The email yielded an above-average click-through rate, which drove more people to the Light Stalking website and increased overall engagement levels.

Impressive, right? And simple. This is a perfect example of how email A/B testing helps you make data-backed decisions.

Best practices for email testing

Email A/B testing seems pretty straightforward, right?

It is, but like any experiment, if you don’t solidify the details and ensure your test is valid, your results may turn out to be useless.

Keep these things in mind when creating your split test:

1 – Identify each variable you want to study

Prioritize your tests. Run split tests for your most important and most frequently sent emails first. And know what you want to fix about your emails before you run tests.

Create a split testing plan where you conduct one email split test a week or one email split test per month.

2 – Test one element at a time

Never test more than one change at a time. Have a control email that remains the same and a variant with one change — like a different color CTA button, or a different coupon offer — you want to test. If you have multiple variables, it’ll become difficult to identify which one caused a positive or negative result.

3 – Record the test results

Keep records of the email split tests you’ve performed, the results of those tests, and how you plan to implement your learnings. Not only will this keep you accountable for implementing changes, it will allow you to look back on what did and didn’t work.

(Video) A/B testing in email marketing: How to send split test campaign with MailerLite

4 – Use a large sample to get as close to statistically significant as possible

Achieving statistical significance means that your finding is reliable. The larger the sample pool for your test, the more likely you are to achieve statistically significant results. You can be more confident that your findings are true.

5 – Make sure your sample group is randomized

Tools like AWeber’s split testing make sure that your sample group is completely randomized.

Setting up an A/B email test

You have the basics of email A/B testing down, so let’s next discuss how to set one up properly.

1 – Determine your goals

First things first: Identify the intentions behind the campaign you want to test.

Your goals will act as your compass when figuring out the details of your email A/B test. Every component of your campaign should trace back to your end goals.

2 – Establish test benchmarks

Once you have defined your goals, take a look at your current email data and examine how your previous email campaigns have fared. From there, use your findings as benchmark numbers.

These numbers will be significant when it comes time to analyze your email A/B test data so you can gauge early success. These numbers should also help you decide on the variables you want to test moving forward.

3 – Build the test

You have your goals and your benchmark data; now it’s time to build your test. Remember to test only one variable at a time.

Bonus: Did you know AWeber Lite and Plus customers can automatically split test their email campaigns (and can test up to three emails at a time)?

4 – How big should your test sample size be?

You want your test list to be large enough that you can gauge how the rest of the subscribers will likely react without using the entire list, but just small enough that you can send the winning version to a large portion of your audience. The goal is to get accurate, significant results, so bigger lists typically work the best.

However, keep in mind that you should be using a sample that represents the whole list, not just a specific segment.

There are many ways to approach this. You can figure out a generic sample size with a calculation that factors in your email list confidence level, size, and confidence interval.

Or, if you’re an AWeber customer, you can manually select the percentage of your list that will receive each version of the split test.

The Ultimate Guide to Email A/B Split Testing | AWeber (14)

Either way, make sure you select a viable percentage of your list to send your test emails to so you have enough data to analyze. Often this is in the 10% to 20% range.

5 – How long should an email A/B test run?

The answer to this question depends on your list size. If you have a large list, then you may only need to send a single email marketing campaign. Bottom line is you want to make sure that you receive enough opens or clicks (depending on the goal of the email campaign) to ensure the results are statistically significant.

You want to make sure that your test results are at least 90% statistically significant in order to confidently conclude that your test is a winner or loser.

Run your test results through an A/B testing significance calculator to determine the percentage of confidence your test results will hold when you implement your test in future campaigns.

Once your test has ended and as you begin analyzing your data, keep detailed notes of your findings. Ask yourself:

(Video) Using A/B Split Testing in Mailchimp

  • What metrics improved?
  • What elements of the email flat-out didn’t work?
  • Were there any patterns that correlated with past tests?

Maintaining records and tracking results will help guide future campaign optimizations.

Put together a testing roadmap or a detailed record of what you’ve tested, the results, and what you plan on testing in the future. That way, you’ll have a detailed account of your tests and won’t leave any stone unturned in the process.

Tracking and measuring A/B test results

With so many elements to test, you might be thinking, “How can I verify that a campaign is successful or that a test yielded helpful data?”

The answer: Think back to your goals. Your goals will tell you what metrics you should pay the most attention to and what you should work on improving – open rate, click rate, delivery rate.

For example, if generating more leads from email campaigns is your goal, you’ll want to focus on metrics like open rate, click-through rate, and form fills.

It’s also important to look at your metrics as a whole to see the big picture of how an email performed. Being able to track that data and refer back to it will also help you optimize future campaigns.

Get started with your own email test

Email A/B testing is imperative to the success and optimization of any email campaign. It allows you to gain real insight that can help you make decisions about existing and future emails.

Email marketing is always changing, and as subscribers’ attention spans seem to get shorter, it’s vital to know what will yield the most success.

The important thing to remember when it comes to creating an email A/B test is that it doesn’t have to be a complicated process. Email A/B testing is designed to deliver powerful, straightforward insights without a bunch of confusing variables.

Not sure about what font to use for the body of the email? Test it. Going back and forth between a few colors for the CTA button? Test it.

The bottom line: You can and should test different variables of your email campaign before launch so you can optimize for success. Just be sure you’re testing only one variable at a time to get the most accurate and useful results possible.

Download your free email planning template

This email marketing planning template (available in both Excel and Google Sheets) is set up so you can quickly and easily measure the performance of all your email sends and tests. Download it today.

AWeber is here to help

Already an AWeber customer? Start executing your A/B testing strategy today. Our email A/B testing tool allows you to test just about any element of your email (subject line, calls-to-action, colors, templates, preheaders, images, copy, and more!).

Not an AWeber customer yet. Then give AWeber Free a try today.

Keep reading:

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How to do ab testing for emails? ›

In your email marketing tool, you simply set up 2 emails that are exactly the same except for 1 variable, such as a different subject line. You then send the 2 emails to a small sample of your subscribers to see which email is more effective. Half of your test group receives Email A and the other half gets Email B.

Which aspect of the email body can be evaluated with a b email testing? ›

A/B testing can be done on all individual elements of an email like subject line, preview text, from name, or on the whole email such as changing the template, long copy vs short copy. In this guide, we will look at what you should test, and tips for running an effective a/b test.

How is the winning email selected in a B testing? ›

In an A/B test you set up two variations of the one campaign and send them to a small percentage of your total recipients. Half of the test group is sent Version A, while the other half gets Version B. The result, measured by the most opens or clicks, determines the winning version.

When it comes to email marketing what do we mean by the terms ab testing? ›

A/B testing email campaigns involves sending two different versions of an email to two randomly segmented halves of the same list to measure how one change affects performance. This change is usually in the subject line but can also be in the body of the email.

Can Mailchimp do AB testing? ›

It's easy to conduct A/B testing in Mailchimp. To get started, create an email campaign like you normally would, select A/B Test when prompted, and choose the audience or contact segment you want. You'll then move on to the Variables step, so you can decide what you want to test.

What are the 5 sections of an email to evaluate? ›

Emails can be broken into 5 major parts: the sender, subject line, salutations, body, and CTA. These pieces make up 99% of emails and provide an optimal format for engaging with clients and optimising conversions.

What are the 4 main parts of an email body? ›

The 4 Essential Parts of an Email Here's the blueprint of a successful business email.
  • The subject line. Arguably the most important component of the email, the subject line is the deciding factor in whether your message is read or deleted. ...
  • The salutation. ...
  • The bit in the middle. ...
  • The ending.
Feb 10, 2013

Which elements of an email delivery can form the base of an A B test? ›

  • Previewing deliveries.
  • Sending proofs.
  • Testing email messages using targeted profiles.
  • Predictive user engagement capabilities.
  • Email rendering.
  • Adding a control group.
  • Using traps.
  • Preparing the send.
Feb 7, 2022

How do you determine a B test winner? ›

In theory, to determine a winner between Variation A and Variation B, you need to wait until you have enough results to see if there is a statistically significant difference between the two.

What is the success rate of a B testing? ›

With A/B testing, there is always a (5%) chance of making a wrong decision, that's why the significance confidence should be at 95%, and not 100%. So, from a mathematical perspective, if your test has about 10 different variations, then your chance of getting a significance false result is close to 50%.

What is a B testing answer? ›

What is A/B testing? A/B testing, also called split testing, is a method of determining which of two versions of a product feature, web page, campaign element, or other asset performs better for a certain goal.

What is a B testing in marketing examples? ›

A/B testing, also known as split testing, is a marketing experiment wherein you split your audience to test a number of variations of a campaign and determine which performs better. In other words, you can show version A of a piece of marketing content to one half of your audience, and version B to another.

What is a B testing in digital marketing? ›

A/B testing, also known as split testing, it's a method of comparing two versions of an email against each other to determine which one performs better. A/B testing is an experiment where two or more variants of an email are shown to users at random.

What is the importance of a B testing while building a newsletter? ›

This is important because it indicates that you have an edge over the brands that don't test their emails. By failing to A/B test, their campaigns are not running at their optimum potential. By A/B testing your emails, you can ensure that your emails are performing at their best.

How do you send a powerful email? ›

12 Tips for Writing Effective Emails
  1. Subject Lines are Important. ...
  2. Use Bullet Points and Highlight Call to Action. ...
  3. Keep it Short. ...
  4. Don't Muddle Content. ...
  5. Be Collegial. ...
  6. Watch Your Tone. ...
  7. Avoid Too Many Exclamation Marks and No Emojis. ...
  8. Avoid Quotes That Could be Offensive to Others.
Oct 17, 2018

What should I write in compose email? ›

  1. Compose a new email message.
  2. Type in the recipient's email address.
  3. Add a subject line.
  4. Write the message.
  5. Add an inline or attached image.
  6. Attach a file or link to it within the message.
  7. Send your message.

What are the 4 C's of email? ›

To help me accomplish that task, I distilled the writing advice I've read and received over the years into the four Cs—clear, concise, correct, and compelling. Below are the points I keep in mind for each.

What are the six rules of email? ›

Rules for email etiquette
  • Use a clear, professional subject line. ...
  • Proofread every email you send. ...
  • Write your email before entering the recipient email address. ...
  • Double check you have the correct recipient. ...
  • Ensure you CC all relevant recipients. ...
  • You don't always have to "reply all" ...
  • Reply to your emails.

What are the 5 C's of email? ›

Remembering to be clear, cohesive, complete, concise, and concrete when communicating will help improve your writing. Of course, these principles also apply to verbal communication, where things like body language and eye contact can sometimes muddle a message.

What are 3 main parts of an email? ›

The From : line lists the email address and the full name of the sender. The Message-ID : line is like a serial number in that it is guaranteed to uniquely identify the mail message. And the To : line shows a list of one or more recipients.

What is the most important part of an email? ›

The subject line is the most important section of your email. If you use the same line repeatedly, customers will stop opening and reading your emails. You should always try to use a subject line that describes the content of your email.

What are the three important parts of an email? ›

Are you looking for the secret of how to write a professional email that is sure to impress not only your bosses' but other colleagues when they read it check out the three parts of email that are crucial when it comes to writing. They are the subject, body, and finally the signature.

Are most winning ab tests illusory? ›

be false positives and 10%, true positives. Of 51 winning tests, over 80% will actually be false.

How long does it take to run an email a B test? ›

Be patient. Letting your tests run long enough will help you be more confident that you're choosing the right winner. We recommend waiting at least 2 hours to determine a winner based on opens, 1 hour to determine a winner based on clicks, and 12 hours to determine a winner based on revenue.

Will an ab test always have a winner? ›

In fact, getting a winner on the first A/B experiment that you run is highly unlikely. Although finding a variation with better conversion is the ultimate goal, no winner A/B tests are not at all time or money wasters. On the contrary, they can be the source of valuable insights for further A/B experiments.

What are some common reasons a B tests fail? ›

Main Reasons Why Your A/B Test Fails
  • Limited Research before running an A/B test. ...
  • Testing changes that are too small. ...
  • Stopping the A/B test too early. ...
  • Not using segmentation. ...
  • Testing wrong elements or not important steps of the funnel. ...
  • Not Running a follow-up A/B test.
Nov 13, 2019

What are the main pitfalls mistakes in AB testing? ›

Ten common A/B testing pitfalls and how to avoid them
  • Pitfall 1: Ignoring the effects of the significance level. ...
  • Pitfall 2: Declaring winners of multiple offer tests with no statistically significant difference. ...
  • Pitfall 3: Ignoring the effects of statistical power. ...
  • Pitfall 6: Stopping tests prematurely.
Oct 3, 2022

What percentage of ab tests fail? ›

A properly designed experiment will be successful no matter how the results turn out, negative, positive or simply flat. While your 'success' rate can happily hover at 10% (and it absolutely will sometimes be lower), you need to ensure that your 'learning rate' is at 100%.

What is the basics of A B testing? ›

The basic A/B testing process looks like this: Make a hypothesis about one or two changes you think will improve the page's conversion rate. Create a variation or variations of that page with one change per variation. Divide incoming traffic equally between each variation and the original page.

What questions should I ask in AB testing? ›

A/B Testing Interview Questions
  • Define the null and alternative hypothesis.
  • Define your north star metric and guardrail metrics.
  • Power analysis — to determine either sample size or minimum detectable effect for your north star metric.
  • Create a test plan.
Mar 31, 2022

What is the difference between split testing and a B testing? ›

The term 'split testing' is often used interchangeably with A/B testing. The difference is simply one of emphasis: A/B refers to the two web pages or website variations that are competing against each other. Split refers to the fact that the traffic is equally split between the existing variations.

Why is it important to a b test your follow up email templates? ›

A/B testing your follow up emails can help you optimize your email strategy and increase your sales results. By testing different elements of your email, such as subject lines, opening lines, call to action, tone, length, and timing, you can identify what works best for your target audience and your goals.

How do you do an AB test for digital ads? ›

To perform A/B testing, also known as split testing, you separate your audience into two random groups. Each group is then shown a different variation of the same ad. After that, you compare the responses to determine which variation works better for you.

How long should ab testing take? ›

Letting your tests run long enough will help you be more confident that you're choosing the right winner. We recommend waiting at least 2 hours to determine a winner based on opens, 1 hour to determine a winner based on clicks, and 12 hours to determine a winner based on revenue.

How do you sample for an AB test? ›

To A/B test a sample of your list, you need to have a decently large list size — at least 1,000 contacts. If you have fewer than that in your list, the proportion of your list that you need to A/B test to get statistically significant results gets larger and larger.

What is the AB test email subject line? ›

A/B testing is a way of comparing how version A of something, like your email subject line, performs compared to version B, within an audience, like your contact list: An email with subject line A is sent to up to 50% of your selected contacts, while a second email with subject line B is sent to an equal portion.

What is the important thing you should check before sending email? ›

Check the subject line and make sure it's on topic and typo-free. The subject line is the most important part of the email.

What is the purpose of email testing? ›

Email testing aims to ensure that an email arrives to the recipient as intended, regardless of browsers, operating systems and devices used to open the email. In addition, it helps you check that everything is in order, including whether the links used are functioning properly.


1. A/B Testing in Gmail - The BEST Way to Run Email Split Tests
2. A/B testing marketing: The Ultimate Guide to A/B Testing marketing for Maximum Results!
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3. A/B Split Testing for Email Campaigns
4. A B Testing your Email Marketing
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5. Split Testing Tutorial: AB Testing That Works (& Makes You More Money)
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6. How to Use A/B Split Testing to Improve Your Email Marketing
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