Key takeaways ✨
- E-mail A/B testing helps entrepreneurs make smarter choices by swapping one factor at a time—like a topic line, CTA, or ship time—and studying what truly resonates with their viewers.
- To get significant outcomes, you want a transparent speculation, a randomized pattern measurement of at the least 10,000 folks, and sufficient time for outcomes to stabilize.
- Keep away from frequent pitfalls like testing too many variables directly, calling a winner too early, or forgetting to doc and roll out your findings.
- When you can create it, you possibly can take a look at it. Play with topic traces, personalization, design, automation timing, or physique copy to optimize engagement and conversions over time.
- Profitable electronic mail advertising applications use A/B testing as an ongoing apply to problem assumptions, experiment rapidly, and apply insights to future campaigns.
At Litmus, we’re continually testing emails. It’s kinda what we’re identified for 😉. More often than not, we’re speaking about pre-send testing—previewing your electronic mail on tons of of electronic mail shoppers and units to see the way it seems earlier than your subscribers obtain it.
However there’s one other sort of testing that’s nearly as necessary: A/B testing.
This takes place after you ship your electronic mail and is normally performed by your electronic mail service supplier (ESP).
When you’re uninterested in making electronic mail advertising choices based mostly on hunches (or making an attempt to get buy-in on your plans), then operating an A/B take a look at can provide you extra perception into how your viewers responds to completely different design, copy, and strategic selections. With a little bit of foresight and planning, you possibly can flip your intestine emotions and concepts into actual knowledge to share with all the workforce. On this submit, we’ll cowl:
Desk of contents
What’s electronic mail A/B testing?
E-mail A/B testing, also called break up testing, is the method of making two variations of the identical electronic mail with one variable modified, like swapping out a topic line or making use of behavioral focusing on. Then, you ship that electronic mail to 2 subsets of an viewers to see which model performs greatest.
In different phrases: electronic mail A/B testing pits two emails in opposition to one another to see which is superior. You possibly can take a look at parts which might be large or small to achieve buyer insights that allow you to do issues like:
- Replace your electronic mail design.
- Find out about your viewers’s preferences.
- Enhance electronic mail efficiency.
You don’t all the time must A/B take a look at your emails, says Camila Espinal, E-mail Advertising Supervisor at Validity. “A/B testing is a superb alternative when engagement is your major aim,” she says. “You’ll need to select campaigns with massive audiences, like your e-newsletter or a promotional ship, and it must be a repeatable marketing campaign the place these insights could be utilized once more.”
A/B testing fuels higher choices for electronic mail entrepreneurs
It’s an additional step so as to add A/B testing to your electronic mail manufacturing course of, however it’s a worthwhile one if you happen to’re making an attempt to maximise income out of your electronic mail advertising program. Says Espinal, “It offers you the information you want so you possibly can step away from taking a shot at nighttime and use actual info to sharpen your campaigns, enhance engagement, and join along with your viewers. You possibly can definitively shift away from what doesn’t work so that you’re not losing your time creating campaigns that your clients or prospects aren’t inquisitive about, and as a substitute double down on the issues that resonate with them.”
It provides a scientific factor to your electronic mail advertising course of so you possibly can show your electronic mail ROI as a substitute of hoping for one of the best. After we requested electronic mail entrepreneurs how they improved the already-great 36:1 ROI from electronic mail advertising, 12% cited A/B testing as a key a part of their technique.
Supply: The ROI of electronic mail advertising infographic
“Typically, you will get actually caught on ‘Oh, it’s what we’ve all the time performed,’” provides Espinal. “Among the finest components of electronic mail advertising is having the chance to attempt one thing new, and use knowledge to measure that influence.”
A/B testing begins with developing with a transparent speculation: What do you suppose will occur if you happen to change factor X? From there, you possibly can check it out and take that info to maneuver ahead with a brand new design or technique that may dramatically influence your backside line.
Espinal provides, “You don’t know what works till you attempt.”
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How you can dodge 5 frequent electronic mail advertising A/B testing errors
Okay, electronic mail geeks. It’s time to place your scientist hat on. For A/B testing, it’s essential to suppose like a scientist—which suggests selecting what you take a look at, while you take a look at, and the way you take a look at very rigorously. Making one among these frequent errors can blow all the take a look at, making you suppose you’ve nailed down a terrific electronic mail advertising technique solely to get caught with the identical—or worse—ends in your subsequent ship.
Keep away from frequent errors like:
1. Testing an excessive amount of at one time
When you attempt to take a look at multiple factor of your electronic mail…how will which factor instantly impacted the result?
The reply is you gained’t. So though you may be tempted to swap out a topic line AND a CTA AND your design in the identical take a look at to pit two emails in opposition to one another, resist the urge! Cautious, incremental testing will get you the place it’s essential to go. “If you wish to take a look at a number of parts, you need to use multivariate testing, however it requires a really massive viewers to make it work,” says Espinal.
This type of test-everything mentality typically comes from a deeper problem: Not having a transparent speculation within the first place. It’s essential to have an outlined aim in thoughts, with the matching metrics to measure, to find out the winner. “Even when one model performs higher, you gained’t be taught why with no robust speculation,” provides Espinal. “It must be an if/then assertion, like ‘If we alter this topic line, then we’ll see extra opens as a result of it creates a way of urgency.’”
2. Working exams with too small a pattern
Whenever you do run a take a look at, it must be with a statistically vital, randomized viewers. Meaning it needs to be massive sufficient and random sufficient the place for positive that no matter adjustments you made had an influence and also you’re not nitpicking between decimal factors.
“With only some hundred contacts, the outcomes gained’t attain statistical significance, so the result is unreliable,” says Espinal. “You need to intention for 10,000 folks or extra on a take a look at if you happen to can. Equally, you possibly can’t assume one model gained simply because it’s barely forward, like 22% opens for model A vs. 21% opens in model B. That’s not a transparent winner.”
An A/B testing calculator may also help decide the required pattern measurement, and if the viewers is simply too small, take a look at solely large, sweeping adjustments or use sequential exams to get a greater sense of what’s working and what’s not. Intention for 95% confidence (p
Then, use your ESP to verify it’s a random break up, quite than testing current segments (like a West Coast vs. East Coast viewers break up) to take away any potential bias from the variations in your viewers. In any other case, you gained’t have the ability to isolate the variable you’re utilizing in opposition to built-in preferences out of your viewers.
3. Funky take a look at timing
You could be concerned to see the outcomes, however an A/B take a look at takes at the least 48 hours to run its course, and even then, you could need to wait longer to realize statistical significance. “It takes some time for folks to get by their inbox,” says Espinal. “Be sure to’re permitting sufficient time for folks to see the e-mail earlier than calling a winner.”
Early outcomes can flip-flop wildly, so that you threat a false optimistic on a variant with out defining the take a look at length up entrance along with your workforce. From there, it’s as much as you to resolve if you wish to run a affirmation take a look at with a future electronic mail or transfer ahead with the outcomes.
Equally, be sure to’re testing exterior of main promotions, holidays, or information occasions to keep away from uncommon habits that may skew the outcomes. “Until you’re testing seasonal messaging, you must all the time attempt to run an A/B take a look at below the situations you need to replicate the ends in,” says Espinal. “Uncommon habits gained’t replicate regular campaigns, so you possibly can’t use the outcomes of that take a look at.”
4. Forgetting about rolling out the outcomes
You’ve put in all that effort to create the take a look at—now be sure to’re documenting and really utilizing the outcomes. “Log the speculation, final result, and perception for each take a look at,” says Espinal. “In any other case, you’ll simply repeat your errors. I maintain a central A/B take a look at log with take a look at particulars and outcomes so I do know what to do for my subsequent marketing campaign.”
Flip the insights that you just get out of your laborious work into playbooks and pointers as you progress ahead with future campaigns. That approach, as a substitute of following the identical “greatest practices” that everybody makes use of, precisely what works on your viewers—whether or not it’s shorter topic traces or chatty ones, sending on Tuesdays or Wednesdays, or making your CTA buttons black as a substitute of orange.
A/B Testing MistakeImpactHow to Keep away from ItTesting an excessive amount of at onceIt’s unattainable to isolate what truly labored.Take a look at just one factor of your emails at a time.Utilizing a pattern measurement that’s too smallWithout randomizing a big pattern measurement, you gained’t obtain statistical significance so you possibly can’t select a winner.Take a look at with random splits of 10,000 folks or extra.Calling a winner too early or throughout “off” timesIt takes time to get the outcomes of a take a look at and attain statistical significance so you possibly can know which model really gained.Wait 48–72 hours earlier than calling the outcome. If there’s a significant information occasion or vacation, wait to run the take a look at.Forgetting concerning the resultsFailing to doc after which roll out these adjustments defeats the aim of operating an A/B take a look at within the first place.Doc your whole learnings and roll out adjustments in future electronic mail campaigns.
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How you can set-up and run efficient electronic mail A/B exams
Whereas electronic mail A/B testing is easy in concept, it could possibly have lots of shifting components. If you wish to get correct insights to share along with your workforce, make investments somewhat time planning and analyzing.
Beneath are the steps it’s essential to take to run a profitable (and insightful) A/B take a look at.
1. Select an goal
As with many initiatives, it’s essential to begin your electronic mail A/B testing with the top aim in thoughts. Select your speculation, what you need to be taught, or what metric you need to enhance.
Whereas you need to use electronic mail A/B testing to enhance campaign-level metrics like open charges, attempt to observe the influence even additional. For instance, how does the conversion charge differ from the completely different emails? Since topic traces set expectations for the content material, you would possibly see their affect additional than the inbox.
2. Choose the variable
As soon as what impact you need to have, it’s time to choose your variable element. Be sure to’re solely testing one variable at a time. If there’s multiple distinction between your management and variable emails, you gained’t know what change moved the needle. Isolating your electronic mail A/B exams could really feel a bit slower, however you’ll have the ability to make knowledgeable conclusions.
3. Arrange the parameters
The third step in your electronic mail A/B testing course of has probably the most choices. Whenever you arrange parameters, you resolve on the entire items that make sure the take a look at is organized. Your choices embody:
- How lengthy you’ll run the take a look at. You’ll most likely be sitting on the sting of your seat ready for outcomes, however it’s essential to wait as much as a day for outcomes to trickle in.
- Who will obtain the take a look at. If you wish to A/B take a look at inside a specific phase, be sure to have a big sufficient viewers for outcomes to be statistically vital.
- Your testing break up. As soon as which segments will obtain the take a look at, you must resolve easy methods to break up the ship. You possibly can do a 50/50 break up the place half will get the management, and the opposite receives the variable model. Or, you possibly can ship management model A to twenty% and take a look at model B to a different 20%, then wait and ship the winner to the remaining 60%.
- Which metrics you’ll measure. Determine precisely which metrics you need and easy methods to get the information earlier than your take a look at. How will you outline success?
- Different confounding variables. Make a remark of variables like holidays that might influence the take a look at outcomes however are out of your management.
4. Run the take a look at
E-mail A/B testing is all about choices, and that features the way you run the take a look at – whether or not for optimizing your lifecycle advertising efforts or enhancing engagement in a single electronic mail advertising marketing campaign. The 2 principal methods to run the take a look at are:
- Arrange the A/B take a look at in your ESP to run robotically. Letting your ESP handle the split-sending might be somewhat simpler to handle and is an effective choice for easy exams (like electronic mail QA) with extra surface-level objectives like rising open charges.
- Manually break up the ship. Organising the 2 separate emails and manually sending the emails is extra hands-on however can provide you a cleaner take a look at knowledge past your ESP (like web site engagement). Use this methodology if you wish to observe outcomes past the marketing campaign. When you’re in the midst of an ESP migration, this may also help with seeing efficiency and have gaps.
5. Analyze the outcomes
As soon as it’s time to investigate the outcomes, you’ll be pleased about each second spent rigorously planning. Because you went in with a transparent concept, what to search for as soon as the take a look at is over. Now it’s essential to evaluate outcomes and share them along with your workforce.
Until you need to take a look at once more. Pay attention, you don’t must, however there’s a probability that your variable electronic mail received a lift from the “shiny new issue.” If you wish to verify the primary take a look at outcomes, you possibly can run the same take a look at (with the identical cohort!) to see if the learnings stay true. Then, doc these findings and make it official for future campaigns.
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What to A/B take a look at in your emails
You possibly can take a look at just about the whole lot in your emails, from format to colours to your copy. “You could just like the look of a white, smooth electronic mail, however it could not resonate along with your viewers as a result of it doesn’t stand out. It’s attention-grabbing to check shade variations, picture variations, whether or not it’s a rounded or sq. CTA button, your personalization selections…you by no means know what could make a distinction till you take a look at,” says Espinal. “These are the tiny adjustments you can also make that contribute to a wholesome electronic mail advertising ecosystem.”
When you create it, you possibly can take a look at it. To get you began, listed below are ten frequent electronic mail parts to A/B take a look at:
1. The inbox envelope: from title, topic line, and preview textual content
One of many parts that informs subscribers about an electronic mail (from the surface) is the from title. When you can experiment with this if you’d like, be sure that it’s all the time clear that it’s out of your firm. Don’t attempt something too off-the-wall that might really feel spammy. For instance, Mailchimp makes use of a number of From names together with “Mailchimp,” “Jenn at Mailchimp,” and “Mailchimp Analysis.”
If you wish to enhance open charges, the topic line is the commonest place to begin. You possibly can experiment with completely different types, lengths, tones, and positioning. For instance, Emerson A/B examined two topic traces for a free trial electronic mail with a white paper:
- Management: Free Trial & Set up: Seize Vitality Financial savings with Automated Steam Lure Monitoring
- Variable: [White Paper] The Affect of Failed Steam Traps on Course of Crops
That individual take a look at revealed a 23% increased open charge for the topic line referencing the white paper.
Whereas the topic line arguably leads the cost in attractive a subscriber to open an electronic mail, it isn’t the one choice you may have. Testing your preheader or preview textual content can even increase open charges.
2. HTML vs. plain textual content
When you largely ship both HTML or plain textual content emails, it may be value seeing if the grass is greener on the opposite facet. Right here at Litmus, we A/B examined these two electronic mail types throughout a number of segments. By a number of exams, we discovered that one of the best messaging varies between clients and non-customers and that plain textual content emails have a agency place in our electronic mail lineup.
HTML:
Ache textual content:
3. Personalization
“First title” is just one type of personalization you possibly can select on your emails. Whereas this methodology can enhance clicks, you possibly can increase your personalization horizons on your A/B exams, together with dynamic content material, interactive parts, or by including (or eradicating) copy about an individual’s location, earlier purchases, buyer standing, and extra.
Supply: State of E-mail Report 2025
After we requested electronic mail entrepreneurs for the 2025 State of E-mail Report what moved the needle probably the most with their personalization, dynamic content material got here in on high, simply after your segmentation technique. When you’re not bought on dynamic content material but, take a look at it.
Espinal likes to check personalization greater than every other factor as a result of it has the most important upside potential. “Probably the most thrilling exams I ran at my earlier firm was a selected nurture for a product by completely different viewers buckets,” she says. “We modified the physique copy of the e-mail and ran A/B exams in opposition to a management for our three segments. It’s additional work however could make a product launch that rather more profitable.”
4. Automation and timing
Most electronic mail A/B testing focuses on what goes in an electronic mail, however it’s also possible to take a look at when to ship it.
For instance, you may alter how lengthy after an individual abandons their cart earlier than you ship them a reminder. One other A/B testing methodology to attempt is what number of emails in a triggered sequence you ship.
That’s true for testing broadcast emails, however automated and transactional emails deserve testing and enchancment, too. Typically, these emails are those doing the heavy lifting of subscriber engagement, so it’s essential to check these always-on emails.
5. Copy, imagery, and design selections
The tone and positioning of your electronic mail copy influence whether or not the message catches a reader’s curiosity or not. A/B testing within the “copy” class covers a ton of parts in your electronic mail, together with physique copy, headlines, and button copy.
Along with the design of an electronic mail, you possibly can mess around with the size of the message. Listed here are a number of inquiries to ask your self:
- Do subscribers need extra content material and context within the message, or simply sufficient to pique their curiosity?
- What size is good for several types of electronic mail? Or completely different units?
- Do all segments favor the identical size of electronic mail?
When you use stylized emails, attempt A/B testing your visuals. Do completely different hero pictures change engagement? Can you employ animated GIFs in longer emails to extend learn time? Does together with an infographic in an electronic mail make folks extra more likely to ahead it? The chances are almost infinite.
A/B Testing ElementWhy Take a look at It?From title, topic line, preview textChanging one among these parts can influence your open charge. And everyone knows that you just don’t get any clicks with out opens.HTML vs. Plain textGet a way of the tone and elegance of your electronic mail designs that resonate probably the most along with your subscribers.PersonalizationPlay round with how a lot to personalize your emails and which parts to personalize, like first title, geolocation, buyer standing, and dynamic product suggestions.Automation and timingNot simply what you ship however while you ship it could possibly influence opens and clicks. This goes on your automated and transactional emails, too.Copy, imagery, and designThere are infinite methods to seek out optimization wins along with your design and duplicate by altering out headlines, physique copy, CTA buttons, and extra.
When NOT to run an electronic mail advertising A/B take a look at
There’s loads of parts you possibly can A/B take a look at…however don’t confuse testing for taking motion.
Espinal says, “Anytime it’s essential to ship a vital communication, or one thing very time-sensitive, that’s not the time to run a take a look at. That features transactional emails, like a affirmation electronic mail or delivery affirmation. Put your vitality elsewhere.”
Crucial factor to remember? That no matter take a look at you run could be repeated. So if you happen to’re considering of doing an A/B take a look at on a random, advert hoc electronic mail marketing campaign since you learn this text and suppose you “ought to,” don’t fear! You don’t have to check each single marketing campaign that you just run. “It’s all about taking that knowledge and replicating that shifting ahead, so if there’s any a part of the marketing campaign that you just simply can’t do this with, save the A/B take a look at for one more time,” provides Espinal.
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How high manufacturers use electronic mail A/B testing to drive outcomes
What does A/B testing appear to be in motion? Right here’s how high manufacturers use it of their common electronic mail advertising cadence, as advised to our electronic mail geeks at Litmus Reside a number of years again:
1. Sq. does incremental testing to isolate their experiments
Tyler Michael, from Sq., makes use of A/B testing incrementally, altering one side of their nurture sequences and newsletters at a time to allow them to isolate precisely what labored or what didn’t. He recommends conventional parts to check, however he typically focuses on timing dimensions you possibly can A/B take a look at like:
- Sending delay
- Timezone localization
- Day of the week
“When you’re ever stunned by the outcomes, run the take a look at once more,” he advises. “There are a number of parts that may influence the validity of your outcomes, like seasonality (vacation vs. summer time), execution (load occasions or errors), or timing (day of week). The longer you run an experiment, the extra possible your significance will stabilize.”
2. Intuit constructed a speedy electronic mail experimentation framework
Rian Lemmer and Kate Tinkleburg from Intuit advocate failing quick and savoring the surprises as a lot as doable for his or her electronic mail advertising program. “We’re speaking about shifting a few hours from concept to experiment within the ‘doing’ part as quick as doable. Typically we even put aside our common jobs to take a few days simply doing experiments so we are able to iterate extra rapidly and construct momentum,” says Lemmer.
“Most significantly, it must have actual metrics behind it,” provides Tinkleburg. Surveys take an excessive amount of time and introduce bias, which is why A/B testing permits them to get from A to Z sooner. “You want to have the ability to see their habits and make adjustments based mostly on that. With electronic mail we now have loads of metrics you need to use, however you want actual buyer foreign money so that they have pores and skin within the recreation or willingness to pay for the experiment to be worthwhile,” she says.
3. Certainly takes A/B testing additional down the funnel
Lindsay Brothers, a product supervisor at Certainly, believes that experimentation is one of the best ways to be taught. “We’re typically unsuitable,” says Brothers. “Job alerts, our hottest electronic mail checklist, hadn’t been examined for years. We examined the copy for the CTA of our kind and completely nobody thought the winner would win. Extra importantly, each single one did higher than the management. We solely stood to achieve by testing this!”
You’d suppose it might be one thing like “subscribe,” or “join,” for his or her CTA to be as clear as doable, however the winner was “activate.” They elevated their electronic mail signups by testing the shape by 12%—an enormous win over time, and the start of A/B testing different elements of their electronic mail advertising program past what’s within the electronic mail itself.
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You will discover A/B testing in just about any ESP nowadays, although the extra options will differ. For instance, at Litmus we use Advertising Cloud Account Engagement (formally Pardot). Right here’s what our setup seems to be like once we run an A/B take a look at:
Whenever you’re evaluating completely different A/B testing choices inside your ESP, take into account:
- Does it let you randomize the viewers? That is key for ensuring you get a statistically vital outcome.
- How straightforward it’s to create two variations of the identical electronic mail to ship on the similar time, particularly if you happen to’re doing one thing extra advanced than topic line exams.
- Whether or not you possibly can flip off ship time optimization so that you’re eliminating as many timing elements as doable—except, in fact, you’re testing timing.
- How the ESP packages up the “winner” variant with further insights, or if it makes use of AI to hurry up the A/B testing course of.
- Integrations the platform has with different analytics instruments, like Litmus Analytics, so you possibly can mix your pre-send testing along with your A/B testing to optimize your electronic mail advertising program even additional.
Whether or not you employ HubSpot, Fixed Contact, Salesforce Advertising Cloud, or one thing else, examine to see what sort of A/B testing options can be found in your ESP. When you’re not proud of what your ESP has to supply, a instrument like Optimizely, Hotjar, or Loopy Egg may also help you. Although initially designed for touchdown pages, they’ve some options you need to use—like a chance calculator—to run your A/B exams on electronic mail campaigns.
Steps earlier than you launch your first electronic mail A/B take a look at
Earlier than you begin your first A/B take a look at, right here’s a abstract of the whole lot it’s essential to learn about electronic mail A/B testing:
StepWhy?For instance…Select an goal and make a speculation.You need to solely take a look at one factor of your electronic mail at a time, and measure it in opposition to the suitable metrics.Topic traces / open ratesRandomize your viewers and select a big sufficient pattern measurement.That you must obtain statistical significance and chance confidence (p10,000 or extra viewers members, random sliceRun the take a look at.This can allow you to make changes to future campaigns. Make sure you select a marketing campaign you possibly can replicate. Variant A: CTA button shade (default, what you all the time do)
Variant B: CTA button shade (new)
Analyze the outcomes, doc your findings, and roll out adjustments to a future marketing campaign.The worth in A/B testing comes from selecting a winner and shifting ahead with these insights.Instance: Variant B (new CTA shade) gained. The following electronic mail has the brand new CTA shade.
Take the guesswork out of electronic mail testing with Litmus
All ESPs provide you with entry to the identical normal electronic mail metrics, and it’s also possible to faucet into issues, like internet analytics, to grasp habits exterior of the inbox. If you wish to dig deeper into your A/B exams with superior metrics, Litmus may also help you do extra pre-send testing, together with electronic mail QA exams.
Listed here are just some use instances the place Litmus E-mail Analytics might enhance your insights:
- Evaluate the learn charges between variations, not simply open charges, to see which topic line model attracted probably the most engaged subscribers.
- Perceive which content material results in the best share charge so you possibly can leverage learnings to develop your referral program.
- Analyze A/B take a look at outcomes between electronic mail shoppers and units, significantly if what you’re testing doesn’t have broad electronic mail consumer assist.
Upon getting your superior analytics experiences and findings, Litmus makes it straightforward to share the outcomes along with your workforce. Then, you possibly can optimize and drive methods in electronic mail and the remainder of your advertising channel combine.
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