Klaviyo lists and segments are a fundamental part of email marketing, but they can be confusing when you're just starting out. At first glance they look pretty similar, and it's easy to get stuck wondering when to use each. The good news: while every account differs, a few simple rules can make a big difference to your deliverability and engagement.

A quick refresher: what are they?

The simplest way to picture it: a segment always lives inside a list. The list is everyone; the segment is a meaningful slice of them.

You can build segments on all sorts of data, depending on what you collect:

When to use a list

Many people assume they should send every campaign to their full list. You can, but it will harm your deliverability:

Remember, even once-engaged customers fizzle out over time. Cleaning your database regularly makes room for people more likely to respond, without ballooning your Klaviyo billing.

When to use a segment

Segments are what you should reach for when sending campaigns. We typically recommend engagement-based segments, since they drive deliverability and lift your metrics across the board, meaning more inbox placement, less spam folder, and stronger sales long term:

When you first start on Klaviyo, you may need a mass send or two to your list to learn who's engaged. That can dent deliverability momentarily. From there, focus on 90-day engagement until your open rates are strong, then gradually widen:

Your list is everyone you could email. Your segment is everyone you should.