Composer, Klaviyo’s AI marketing agent, can build email and SMS content A/B tests within a campaign conversation. The guide covers what to test, how to isolate differences between versions, and which setup requirements and review steps apply before sending.
Campaign test options: Compare subject lines, preview text, approved sender names, email content and design, or SMS copy.
Focused test design: Test one idea at a time while keeping the audience, offer and send time steady across versions.
Channel setup requirements: SMS and image messages require a sending number and channel setup in your Klaviyo account.
Review before sending: Composer leaves campaigns as drafts, so check both versions for accuracy, links, offers and test settings before scheduling or sending.
Learn from results: Ask Composer which version won and use the winner in your next campaign.
Stop guessing what your audience wants. Composer, Klaviyo’s AI marketing agent, can set up email and SMS A/B tests as part of your campaign, so you go from campaign idea to test in one conversation.
Test subject lines, preview text, sender names, email content and design, or SMS copy. With Composer, you can be up and running in one conversation. Pick a play below, paste the prompt, and make it yours.
Pick your campaign A/B test play
Play
Use it when
What you get
Subject line and preview text
You want more people to open
Two inbox versions to compare, built into the campaign
Sender name
You're not sure who the email should come from
Your brand name tested against another sender name you approve
Email content and design
You want more people to click
Two versions with different headlines, images, buttons, layouts or products
SMS copy and format
You want more text responses
Two SMS versions, or SMS tested against an image message
1. Test your subject line and preview text
This is the one to start with. The subject line and the preview text beside it decide whether someone opens your message. Give Composer two angles and it will set up the test.
Ask Composer
text
Create an A/B test for my next campaign. Test two subject lines: one leading with the 20% discount, one leading with the new fall arrivals. Keep everything else the same.
What you can do with it
Compare messaging angles. Urgency against curiosity, offer against product, short against descriptive.
Test the preview text too. Try different inbox text beside the same subject line.
Start from what you have. Ask Composer to build the test into a campaign you're already drafting in the same conversation.
2. Test the sender name
Who the email comes from can matter as much as what it says. Test your brand name against another sender name, like a founder or a team name.
Ask Composer
text
For this campaign, test the sender name: our brand name against 'Maya from [Brand]'. Keep the subject line and content the same.
Only test sender names you've approved and set up for sending.
3. Test email content and design
Once people open, the content within your message decides whether they click. Compare headlines, images, button wording, layouts or the products you feature.
Ask Composer
text
Create two versions of this email for an A/B test. Version A leads with a lifestyle image and the button 'Shop the collection'. Version B leads with our three best sellers and the button 'Find your fit'.
Change one or two things at a time, so you know what made the difference.
4. Test your SMS message
Texts are short, so every word counts. Test different copy, a different call to action, or a text-only message against an image message.
Ask Composer
text
Set up an SMS A/B test for our weekend sale. Version A is a short text with the code. Version B is an image message showing the hero product with the same code.
Check message length, links and any restricted content in both versions before you send.
Know the limits before you test
Tests cover campaign content. Composer sets up email and SMS content A/B tests: subject lines, preview text, sender name, email content and design, and SMS content.
Campaigns are still drafts. Composer doesn't send or schedule anything on its own. Review both versions and the test settings before you send.
Set up each channel first. SMS and image messages need a sending number and the channel set up in your Klaviyo account.
Use approved sender names. Only test sender names your team has approved and can send from.
Review before you rely on it. Composer can be wrong. Check both versions for accuracy, links and offers.
Get better results
Test one idea at a time. If both versions change the headline and the image, you won't know which one worked.
Name the difference. ‘Discount-led subject line vs. product-led’ beats ‘make two versions’.
Keep everything else the same. Ask Composer to hold the audience, offer and send time steady across versions.
Say what you're trying to move. Opens for subject lines and sender names, clicks for content, responses for SMS.
Keep it in one conversation. Build the campaign and the test together so both versions stay on-brand.
A rhythm that works
Brief. Describe the campaign and what you want to test.
Build both versions. Ask Composer for version A and version B in the same conversation.
Review. Check copy, links, offers and the test settings in both.
Send. Schedule the campaign when you're ready.
Learn. Ask Composer which version won, then use the winner in your next campaign.
If something looks off
Both versions look the same. Tell Composer exactly what should differ between A and B.
Too much changed between versions. Ask Composer to keep everything identical except the one element you're testing.
The SMS test won't build. Check that SMS is set up in your account with a sending number, then ask again.
The sender name isn't right. Give Composer the exact approved sender name to use.
Get started with A/B testing in Composer
Open Composer and ask it to create an A/B test for your next campaign. Start with the subject line, and then keep testing.
# AI A/B Testing for Campaigns: Email and SMS Tests From a Prompt
## The marketer's guide to A/B testing in Composer
Stop guessing what your audience wants. Composer, [Klaviyo’s AI marketing agent](/uk/composer), can set up email and SMS A/B tests as part of your campaign, so you go from [campaign idea](https://help.klaviyo.com/hc/en-us/articles/52308788113307) to test in one conversation.
Test subject lines, preview text, sender names, email content and design, or SMS copy. With Composer, you can be up and running in one conversation. Pick a play below, paste the prompt, and make it yours.
## **Pick your campaign A/B test play**
| Play | Use it when | What you get |
| --- | --- | --- |
| Subject line and preview text | You want more people to open | Two inbox versions to compare, built into the campaign |
| Sender name | You're not sure who the email should come from | Your brand name tested against another sender name you approve |
| Email content and design | You want more people to click | Two versions with different headlines, images, buttons, layouts or products |
| SMS copy and format | You want more text responses | Two SMS versions, or SMS tested against an image message |
## **1. Test your subject line and preview text**
This is the one to start with. The subject line and the preview text beside it decide whether someone opens your message. Give Composer two angles and it will set up the test.
```json
{
"_key": "32c4a3f1d814",
"_type": "codeSnippet",
"code": "Create an A/B test for my next campaign. Test two subject lines: one leading with the 20% discount, one leading with the new fall arrivals. Keep everything else the same.",
"filename": "Ask Composer",
"language": "text",
"theme": "dark-plus"
}
```
**What you can do with it**
- **Compare messaging angles.** Urgency against curiosity, offer against product, short against descriptive.
- **Test the preview text too.** Try different inbox text beside the same subject line.
- **Start from what you have.** Ask Composer to build the test into a campaign you're already drafting in the same conversation.
## **2. Test the sender name**
Who the email comes from can matter as much as what it says. Test your brand name against another sender name, like a founder or a team name.
```json
{
"_key": "86d5ed686af9",
"_type": "codeSnippet",
"code": "For this campaign, test the sender name: our brand name against 'Maya from [Brand]'. Keep the subject line and content the same.",
"filename": "Ask Composer",
"language": "text",
"theme": "dark-plus"
}
```
Only test sender names you've approved and set up for sending.
## **3. Test email content and design**
Once people open, the content within your message decides whether they click. Compare headlines, images, button wording, layouts or the products you feature.
```json
{
"_key": "68536b6bb3b5",
"_type": "codeSnippet",
"code": "Create two versions of this email for an A/B test. Version A leads with a lifestyle image and the button 'Shop the collection'. Version B leads with our three best sellers and the button 'Find your fit'.",
"filename": "Ask Composer",
"language": "text",
"theme": "dark-plus"
}
```
Change one or two things at a time, so you know what made the difference.
## **4. Test your SMS message**
Texts are short, so every word counts. Test different copy, a different call to action, or a text-only message against an image message.
```json
{
"_key": "f0ff924ffcd0",
"_type": "codeSnippet",
"code": "Set up an SMS A/B test for our weekend sale. Version A is a short text with the code. Version B is an image message showing the hero product with the same code.",
"filename": "Ask Composer",
"language": "text",
"theme": "dark-plus"
}
```
Check message length, links and any restricted content in both versions before you send.
## **Know the limits before you test**
- **Tests cover campaign content.** Composer sets up email and SMS content A/B tests: subject lines, preview text, sender name, email content and design, and SMS content.
- **Campaigns are still drafts.** Composer doesn't send or schedule anything on its own. Review both versions and the test settings before you send.
- **Set up each channel first.** SMS and image messages need a sending number and the channel set up in your Klaviyo account.
- **Use approved sender names.** Only test sender names your team has approved and can send from.
- **Review before you rely on it.** Composer can be wrong. Check both versions for accuracy, links and offers.
## **Get better results**
- **Test one idea at a time.** If both versions change the headline and the image, you won't know which one worked.
- **Name the difference.** ‘Discount-led subject line vs. product-led’ beats ‘make two versions’.
- **Keep everything else the same.** Ask Composer to hold the audience, offer and send time steady across versions.
- **Say what you're trying to move.** Opens for subject lines and sender names, clicks for content, responses for SMS.
- **Keep it in one conversation.** Build the campaign and the test together so both versions stay on-brand.
## **A rhythm that works**
1. **Brief.** Describe the campaign and what you want to test.
2. **Build both versions.** Ask Composer for version A and version B in the same conversation.
3. **Review.** Check copy, links, offers and the test settings in both.
4. **Send.** Schedule the campaign when you're ready.
5. **Learn.** Ask Composer which version won, then use the winner in your next campaign.
## **If something looks off**
- **Both versions look the same.** Tell Composer exactly what should differ between A and B.
- **Too much changed between versions.** Ask Composer to keep everything identical except the one element you're testing.
- **The SMS test won't build.** Check that SMS is set up in your account with a sending number, then ask again.
- **The sender name isn't right.** Give Composer the exact approved sender name to use.
## **Get started with A/B testing in Composer**
Open Composer and ask it to create an A/B test for your next campaign. Start with the subject line, and then keep testing.