Open your phone. Look at your inbox. What do you see?
For most subscribers, the answer is: a sender name, a subject line, and then a second line of text that's almost as prominent. On iOS Mail it's a full second row in gray. On Gmail mobile it's right there next to the subject. On dark mode it stands out even more.
That second line is the preview text. And if you're not writing it on purpose, you're probably losing opens.
The shift nobody announced
For years, subject lines were the whole game. You'd A/B test "50% off everything" versus "Our biggest sale yet" and watch the open rates wiggle by half a point. Preview text was an afterthought, often left blank, often defaulting to "View this email in your browser" or whatever junk lived at the top of your template. But the old subject line playbookisn't enough anymore.
Then mobile inbox UI changed. Slowly at first, then all at once. Apple Mail started showing two lines of preview by default. Gmail did the same on mobile. Outlook caught up. Today, the average inbox preview gives roughly the same visual weight to your subject and your preview text.
Look at your own inbox behavior. When you decide whether to tap an email, are you reading just the subject? Or are you scanning both lines together?
You're scanning both. So is everyone else.
What most brands put there
Walk through your last ten campaigns. Pull up the preview text field in Klaviyo. What's there?
If you're like most DTC brands, you'll find one of these:
- Blank (so it pulls the first line of your email, usually "Hi {first_name}" or your header text)
- A repeat of the subject line in slightly different words
- A generic teaser like "Don't miss out" or "Limited time"
- "View in browser" because the template defaulted to it
None of these are doing work for you. The blank one is actively bad. If your first line of email body is "Hi friend, we wanted to let you know..." then that's what shows up in the inbox preview. You're using premium real estate to say nothing.
The job of preview text
Subject lines hook. Preview text confirms.
Your subject line creates the question. Your preview text answers it just enough to make the open feel worth it. Together, they're a one-two punch. Apart, they're just two attempts at the same job.
Think of it like a movie poster. The title makes you curious. The tagline tells you what kind of movie it is. You need both to commit two hours of your life.
Here's a quick example. Subject line: "We owe you an apology." That's a hook. It makes you want to know more. Now imagine the preview text is "Don't miss our biggest sale ever." That's a bait and switch, and your subscriber feels it in half a second. They don't open, and now they trust your subject lines less.
Compare that to: Subject line: "We owe you an apology." Preview text: "Your order shipped late last month. Here's what we're doing about it." Now the subject and preview agree. The reader knows what they're getting into. They open because they want the rest of the story.
What good preview text actually does
The best preview text does one of four things:
- Adds the specific. Subject says "New drop." Preview says "Three colorways, sold out in 48 hours last time."
- Adds the urgency. Subject says "Last call." Preview says "Cart closes at midnight ET, no extensions."
- Adds the proof. Subject says "Customers can't stop emailing us about this." Preview says "Over 800 five-star reviews in two months."
- Adds the surprise. Subject says "About that price increase." Preview says "We're not raising prices. Here's why."
Notice what's not on this list: repeating the subject in different words. Repeating the subject doubles the hook and leaves zero room to give the reader a reason to act.
The 60 character rule
Most inboxes truncate preview text somewhere between 50 and 90 characters depending on device. The first 60 are basically guaranteed to show. After that you're rolling the dice.
So write the punchy version first. Don't bury the verb in a long subordinate clause. Don't start with "Welcome to our weekly roundup of..." because the inbox will cut you off mid-thought.
A good test: write your preview text, then chop the first 60 characters and read just those. Do they stand on their own? If yes, you're good. If they read like a fragment, rewrite.
The Klaviyo workflow that keeps this consistent
The mechanical part is easy. In Klaviyo's campaign editor, scroll down past the subject line. There's a Preview Text field. Type it there. Done.
The hard part is doing it for every send, with intention, every time. When you're scheduling four campaigns a week, the preview text is the first thing that gets phoned in. You write the subject, you check the segments, you set the send time, and then you tab past preview text because the deadline is now.
This is where most brands lose the gains. Not because they don't know preview text matters, but because the workflow doesn't force them to think about it. If you're planning campaigns ahead, build preview text into your planning template from day one.
A few things that help:
- Make preview text a required field in your campaign brief, not a "we'll do it last" item.
- Pair subject and preview as one unit during planning. Don't write subjects in isolation.
- Save a swipe file of preview text formats that worked. Reuse the patterns.
- Review the preview rendering on mobile before you hit send. Klaviyo's preview tool shows it.
The calendar view problem
Here's something most teams don't notice until they fix it. When you're planning your next two weeks of campaigns in a list view or a spreadsheet, you see the subject lines. You don't see the preview text. So you start optimizing the visible thing and ignoring the invisible thing. This is exactly why a visual calendar changes how you plan.
This is part of why we built Cadento with both fields visible on the calendar view. When you're laying out your sends for the week, you should be looking at the subject and preview text together. They work as a pair. Planning them separately is how you end up with mismatched hooks and weak inbox presence.
If you're stuck in a spreadsheet workflow, at minimum add a Preview Text column right next to Subject. Force yourself to fill it in at the same time. It's a small change that pays off fast.
The takeaway
Subject lines still matter. Nobody's saying they don't. But treating preview text as decoration is a mistake your competitors are probably already making, and it's a cheap edge to take from them.
Spend ten extra seconds on every campaign. Write the preview text on purpose. Make it add something the subject doesn't say. Check the first 60 characters.
That's it. No new tools, no new strategy, no new platform. Just one more line of copy that actually does work.
If you want to see how your subjects and previews stack up across a month of campaigns, try Cadento free. The calendar view makes it obvious in about thirty seconds where you've been phoning it in.