Can segmentation approaches be A/B tested?

Yes, segmentation strategies absolutely can be A/B tested. And honestly, they should be. A segment is just a hypothesis: "these people are different enough that they deserve different treatment." Testing is how you find out if that hypothesis holds up.

There are two distinct things you can test, and it helps to be clear on which one you're doing before you start.

Test 1: Does targeting this segment at all actually help?

This is the foundational test. Take a segment (say, customers who bought in the last 90 days) and split them randomly. Half get the segment-specific message you crafted for them. The other half get your standard broadcast email. If open rates, clicks, and conversions are higher for the segment-specific group, targeting is working. If the numbers are the same, your segmentation criteria might need rethinking.

Test 2: Does your segmentation criteria actually matter?

Here you're comparing different ways to slice your list. Maybe you've been segmenting by demographics (location, age) but you want to know if behavioral data (last purchase, pages visited) produces better results. Run both approaches in parallel on comparable audiences and measure which one drives more engagement and revenue. This kind of test takes longer to set up but it's worth it if you're investing in a major segmentation overhaul.

Test 3: Does the content you made for a segment actually resonate?

Sometimes the segment definition is fine but the content itself is the variable. You've already decided to send a dedicated email to recent buyers. Now you're testing whether version A (product-focused) or version B (educational) performs better with that group specifically. This is a classic A/B test, just run within a segment rather than across your whole list.

What to measure

For segmentation tests, you'll want to look beyond open rate. Track click-through rate, conversion rate, revenue per email sent, and unsubscribe rate. Open rate alone tells you whether your subject line worked, not whether your segmentation strategy worked. Revenue per email sent is probably the most honest signal of whether targeting is actually paying off.

A few things to get right before you start

• You need a real control group. Random assignment matters here. If you cherry-pick who gets targeted, you can't trust the results.
• Segmentation tests generally need more time and volume than a simple subject-line test. You're looking for behavioral differences, and those can take a few send cycles to show up clearly.
• Most platforms like Mailchimp, Klaviyo, and Brevo have built-in A/B testing tools. For segmentation tests specifically, you might need to manually set up comparison groups rather than using the standard A/B send feature, since you're often comparing segments rather than message variants.

Now once you find a segmentation approach that works, keep testing it over time. Subscriber behavior shifts, and what worked six months ago won't necessarily hold forever.

So if you want to go deeper, the next question worth reading is how to test the effectiveness of different segments, which gets into the mechanics of setting up comparison groups properly.