You craft a perfect subject line. You spend 20 minutes on it. You A/B test it. You pat yourself on the back. Then you hit send and watch your open rates tank.

What happened? Your preheader happened. That little snippet of text right next to—or below—your subject line in the inbox probably read: “View this email in your browser” or “Having trouble reading this email?” You just handed your reader a perfect reason to ignore you.

The preheader is prime real estate. When you waste it, you undermine every ounce of effort you put into the subject line.

The Silent Saboteur of Your Open Rates

Most readers scan their inbox on mobile. On an iPhone, the preheader shows up as the second line of text under the subject. On Gmail in a browser, it sits right next to the sender name. It’s the second thing people see, and it either reinforces your subject line or kills it.

When your preheader repeats the standard default text, you’re telling the reader: “This email is generic. This company didn’t think about me.” In a crowded inbox, that’s a death sentence.

The Default Text Trap

I once consulted for a SaaS company that had a 22% open rate on their weekly newsletter. They blamed the content. I looked at their email setup. Every single email had the same preheader: “Email not displaying correctly? View it in your browser.”

We changed it to something that expanded on the subject line. For a subject line reading “Your weekly SaaS roundup,” we used the preheader: “3 new features, 1 major bug fix, and a tip from our CTO.” The open rate jumped to 34% in two weeks.

How to Write a Preheader That Works

Your preheader should complete the thought your subject line starts. If your subject line is a headline, your preheader is the subheadline. It should add context, create curiosity, or deliver a specific benefit.

The Three-Second Rule

You have about three seconds in the inbox to earn a click. Your subject line grabs attention. Your preheader seals the deal.

Do this: Subject line: “Your order is on its way.” Preheader: “Track your package and see the estimated delivery date.” Don’t do this: Subject line: “Your order is on its way.” Preheader: “View this email in your browser.”

The first preheader gives the reader a reason to open. The second gives them a reason to delete.

The Preview Text Hack

Most email service providers let you set a custom preheader. Use it. Keep it under 100 characters for desktop and under 50 characters for mobile. Test how it looks on both platforms.

I recommend writing your preheader before you write the body of the email. That forces you to clarify the core message. If you can’t summarize the value in 50 characters, your email probably isn’t focused enough.

The Forward-Looking Takeaway

Stop treating the preheader as an afterthought. Next time you build an email campaign, write the subject line and preheader as a single, cohesive unit. Paste the default text into your template and then delete it immediately. Replace it with something that makes your reader think, “I need to see what’s inside.”

The inbox is a battlefield. Don’t let a lazy preheader be the reason your army loses the first skirmish.