How to Easily Run Email A/B Tests with Klaviyo

In this article, we'll walk you through how to run A/B tests for email campaigns.

Just like with ads and landing pages, you can A/B test subject lines and email copy — but many people assume it's complicated or time-consuming, so it often goes untried.

In reality, email A/B testing is incredibly straightforward, and simply changing a subject line or the body copy can have a significant impact on performance. Here, we'll show you how to run A/B tests using Klaviyo, one of the most popular email marketing apps for Shopify.

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Step 1: Create Your Email

To run an A/B test, start by creating the first version (Pattern A) of your email. You create emails the same way as usual — through Campaigns or Flows. In this guide, we'll walk through the process for sending a broadcast campaign via Campaigns.

Setting Up the A/B Test

After creating and saving your email content, you'll see a "Create A/B Test" section on the screen just before the review page — click on it.

This will open the A/B test configuration screen.

Open the Pattern B section and edit the subject line or email content to create the second variation for your A/B test.

You can also run a test that only changes the send time without modifying the content. This is useful when you want to measure — under fair conditions — whether morning or evening sends yield higher open rates and click rates.

Configuring the Test Metric and Distribution Ratio

Under Content Test Settings, you can choose whether to use open rate or click rate as the test metric. You can also set the distribution ratio, which defaults to 50%:50%.

You can also run an A/B test against a subset of your list, then send the winning content to the remaining recipients.

In the example below, both Pattern A and Pattern B are sent equally to 50% of the total list. The remaining 50% then receives only the better-performing version. The system is also configured to determine the winning email 6 hours after sending.

That's all the setup you need. Now just send the email and wait for the results.

Executing CRM Strategy at Scale with StoreHero

StoreHero helps Shopify merchants who are looking to grow their sales by executing growth initiatives with precision and consistency.

For CRM in particular, we leverage the StoreHero growth platform to deliver highly targeted email, LINE, and on-site product recommendations and offers — driven by customer purchase history, demographic data, and product/SKU performance and inventory data. This enables the kind of granular, high-volume campaign execution that's simply not feasible with manual operations, supporting continuous, sustainable growth.

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Summary

In this article, we introduced how to run A/B tests using Klaviyo, a popular email marketing app for Shopify.

Email is a powerful tool for lead nurturing of prospects and improving LTV (Lifetime Value) of existing customers — and by continuously refining your approach through testing, you can make it an even more effective asset.

Start A/B testing your emails today and discover the winning formula for your store.