receives compensation from some of the companies listed on this page. Advertising Disclosure

What Is A/B Testing in Email?

Jamie Johnson
Jamie Johnson Contributing Writer
Updated Sep 22, 2022

A/B testing lets you see which iterations of the same content get the most engagement from your target audience. This can help you boost your click-through and conversion rates.

As a business owner, you know how important it is to build an email list and engage in email marketing. But you may also be wondering how to send more effective emails. How can you increase the number of subscribers who are opening your emails, engaging with your content and clicking on your links? The answer is to start A/B testing your email campaigns.

What is A/B testing?

A/B testing is also referred to as split testing, and it is the process of sending two versions of an email to your subscribers. The emails are nearly identical, with just one variable changed.

For example, you could use a button for the call to action at the end of one email, and a hyperlink for the CTA in the other email. From there, you’ll examine your results to see which email performed better.

If you’re new to A/B testing, you can start small. Once you get going, you’ll begin to uncover a wealth of data about your email subscribers.

Email A/B testing can help you discover these insights and more:

  • Which subject lines resonate with your audience the most
  • Whether using a button or a hyperlink improves your click-through rate (CTR)
  • Whether your subscribers prefer images or plain text emails
  • If personalizing the subject line increases your open rates

If you want to increase conversions and improve your email marketing strategy, A/B testing your email campaigns is a must. Fortunately, getting started is relatively easy. [Read more about email marketing services here.]



Editor’s note: Looking for the right email marketing solution for your business? Fill out the below questionnaire to have our vendor partners contact you about your needs.

Benefits of A/B testing

A/B testing might feel tedious at first, but the benefits far outweigh the downsides. The biggest advantage of A/B testing is that it shows you what works and doesn’t work with your subscribers.

Imagine if you could go into your next email campaign knowing exactly what to say to your subscribers. You know the type of subject line that will encourage them to open the email. You know how long the email should be and the type of content to include. You know where to place your CTA and how to make it as effective as possible. You also know when to send the email for maximum open rates and what day of the week your subscribers will be the most engaged.

All of this information is possible with ongoing A/B testing. By A/B testing your email campaigns, you can discover the most effective strategies for engaging with your audience.

How does A/B testing email work?

For an A/B test, you’ll send out two versions of the same email, changing just one element between them. For example, you could test different subject lines, email lengths, or times of day to send the email.

Monitor the results to determine which version resonated with your audience the most. This information allows you to make more informed decisions about your email campaigns in the future.

What should you A/B test in email?

One of the biggest reasons many business owners avoid A/B testing is that they aren’t sure what to test. The list of variables you can test are endless, so it’s hard to know where to begin. Let’s look at seven elements you could test first.

Subject line

The subject line is one of the most significant factors in an email’s open rate. It’s what draws your readers in and makes them decide whether to open your email.

There are multiple variables you can test for your subject lines. You can test different lengths for the text and try varying the tone and voice. You could also experiment to see whether questions or statements increase open rates.

You can also see if adding the recipient’s first name to individual subject lines increases your open rates. Since the jury is out on whether subscribers like emojis in the subject line, this could be another item you A/B test. 

Sender name

Many businesses don’t give much thought to the sender name they use when they email their subscribers, but it can have a significant effect on your open rates. Using a personal name instead of a company name often increases open rates – but you want to see if that’s true for your audience before you send out an entire campaign that way. So, with a small group of subscribers, conduct an A/B test using a brand name as the sender versus a personal name in the sender field and see which email gets the highest open rates.


It’s a good idea to see what kind of email template your subscribers prefer. You can try out different color palettes to see which one performs the best. You could test HTML emails versus plain text emails. If you include images, try varying their size and placement in your email. Images in an email can either help or hurt your brand, so find out which types of images your subscribers prefer.

First sentence

Another variable you can test is the first sentence of your email. The first sentence sets the tone for the entire message, and it also shows up as preview text in your subscriber’s inbox. Depending on the mail apps they use, your subscribers will usually see the first 40 to 90 characters, so use every word wisely; play with different words and phrases in your test emails. Getting this sentence right could improve your open rates by 45%.

Time of day

The time of day when you send an email is a big factor in an email marketing campaign’s success. Once they’ve had an email for 24 hours, the chance of a subscriber opening it drops below 1%, so you need to send it when they’re likely to see it as soon as possible.

To find the best time to send an email to your subscribers, test your campaign at different times throughout the day. For instance, you could send the email to one group in the morning and to another group in the early afternoon. It’s impossible to find one perfect hour of the day, but you can get a sense of whether mornings, afternoons or evenings work best for your subscribers.  

Day of the week

The days with the best response rates can vary greatly by industry. For instance, if you sell e-commerce products and target a B2C audience, you might see higher engagement on the weekends, while a B2B audience is likely to be more engaged during a weekday when they’re working.

Send out test campaigns to see whether your open rates are higher on weekends or weekdays. From there, you can test different days against one another.  

Call to action

Your CTA is arguably the most important part of your email because it motivates your audience to click through or convert. Try out different CTA variables to see what works best with your subscribers.

You can start by seeing whether subscribers are more likely to click on a button or a hyperlink. From there, see if changing the color of the link or button makes a difference. You could also vary the placement of your CTA. For instance, if you usually send long-form emails, try placing multiple buttons throughout the email.

You could also vary the wording and tone slightly to see what resonates with your subscribers the most. If you continue to A/B test your CTA and track the results, you’ll learn how to send high-converting emails.

How to A/B test email effectively

Now it’s time to set up your A/B test with your current email provider. This process will vary slightly by email provider, but it should be pretty straightforward. Let’s look at the four steps you’ll take to A/B test your email subscribers.

1. Pick a variable to test.

You’ll start by deciding which variable you want to test with your audience. This will largely depend on which metric you want to improve in your email marketing campaigns.

For instance, if you’re trying to improve your email open rates, you may want to test two different subject lines. You could also see if using a personal name versus a company name in the sender line makes a difference.

If you’re trying to improve your click-through rate, you can test whether a button or a hyperlink for your CTA works better, or if changing the position of the CTA makes a significant difference.

2. Create two versions of the same email.

Next, you’ll create two different versions of the same email. For instance, let’s say you want to see which subject line improves your open rates. You’ll come up with two different subject lines to test with your audience. Then, you can begin setting up an A/B test with your email service provider.

3. Choose your testing groups.

Next, you need to choose your two testing groups. The size of your testing groups will depend on your total number of subscribers and the purpose of the campaign. In many instances, you might want to test your entire list of subscribers. This will give you the most accurate picture of what works best with your audience. In other cases, you’ll want to test a smaller portion of your list.

For instance, if you’re testing a new offer with your audience, you want to get as many conversions as possible. So, you might want to start by testing it out with a small portion of your list until you’re sure of what works.

But how do you know the right sample size? Here’s a good rule of thumb: If your email list is over 1,000 subscribers, you should test 20% of your audience. That means you’ll send one subject line to 10% of your list, and another 10% will receive the email with the second subject line.

4. Analyze and implement your results.

Now it’s time to wait and then analyze your results. Your email service provider should be able to tell you which subject line performed the best. Once you know which subject line was the most effective, you can send an email with that subject line to your entire list.

Of course, your work isn’t done at this point. You should continue to A/B test your email campaigns going forward. The most important thing to keep in mind is that you should only test one variable at a time. This way, you can see a clear difference in each email’s performance, whereas if you test multiple variables in one email, you’ll never know what truly made the difference in your results.

Image Credit: ijeab / Getty Images
Jamie Johnson
Jamie Johnson Contributing Writer
Jamie Johnson is a Kansas City-based freelance writer who writes about finance and business. She has also written for the U.S. Chamber of Commerce, Fox Business and Business Insider. Jamie has written about a variety of B2B topics like finance, business funding options and accounting. She also writes about how businesses can grow through effective social media and email marketing strategies.