Your subject line gets the glory, but it is not working alone.
In most inboxes, subscribers see two pieces of copy before they open: the subject line and the preheader text. Together they form a one-two punch that decides whether the email gets opened or ignored.
Preheader text is the preview snippet that appears after or below the subject line. Some marketers call it preview text, a Johnson box, or the second subject line. Whatever the name, it is valuable inbox real estate — and many campaigns waste it.
This guide covers how long it should be, how to write it, and the common mistakes that send your preview text to waste.
What Is Preheader Text?
Preheader text is the short line an email client displays alongside the subject line in the inbox list.
For example:
Subject: The 2026 email metrics report is ready
Preheader: Open rates, click rates, benchmarks by industry — download inside
The preheader adds context the subject line could not fit. It answers the subscriber's next question: What is actually in this email?
On desktop, preheader text often appears to the right of the subject line. On mobile, it usually appears below it. That difference matters when you decide how much copy to write.
Why Preheader Text Matters
The inbox is a competition for attention. Your email sits next to dozens of others, each fighting for the same glance. A subject line alone is rarely enough to explain the value inside.
Preheader text gives you a second chance to persuade. It can:
- Add a benefit the subject line could not include.
- Create urgency with a deadline.
- Provide social proof or a specific detail.
- Clarify the email's purpose for subscribers who are skim-reading.
In our guide to why some subject lines feel impossible to ignore, we explain how the best hooks combine curiosity with clarity. Preheader text is where clarity usually lives.
How Long Should Preheader Text Be?
There is no universal character limit. The visible length depends on the device, the email client, the subject line length, and whether the email is read in portrait or landscape.
| Environment |
Typical visible preheader |
| iPhone Mail |
70–100 characters |
| Gmail app |
50–90 characters |
| Gmail desktop |
100–150 characters |
| Outlook desktop |
40–80 characters |
The safest rule is to front-load the most important words in the first 40 to 50 characters and keep the total under 100 characters for full visibility on most screens.
You can use an email subject line character counter to check your subject length, then write your preheader to complement it.
How to Write Preheader Text That Works
The best preheaders do not repeat the subject line. They add something new.
1. Expand on the Subject Line
If the subject line asks a question, the preheader can hint at the answer. If the subject line announces a sale, the preheader can add the deadline or the best deal.
Subject: Last call for the September discount
Preheader: 30% off ends tonight at midnight — shop the new collection
2. Lead With the Benefit
Subscribers open emails that promise something useful. Put the clearest benefit first.
Preheader: Save 4 hours a week with this reporting template — download free
3. Add Urgency or Scarcity
A deadline in the preheader can nudge someone who was on the fence.
Preheader: Only 47 seats left — register before they are gone
4. Use a Micro-Call-to-Action
Tell the reader what to do next, even before they open.
Preheader: Tap to see your personalised recommendations
5. Create Curiosity Gaps
Curiosity works when paired with relevance. A good preheader teases without being vague.
Preheader: The one metric we stopped tracking — and why open rate followed it
That line nods to our article on why email open rate is a misleading metric.
Common Preheader Mistakes
A few patterns appear again and again in underperforming campaigns.
Repeating the Subject Line
If the preheader says the same thing as the subject line, you have wasted half your preview. The two should work together, not echo each other.
Leaving It Blank
When you do not set a preheader, the email client pulls the first text it finds. The result is usually alt text, navigation links, or "View in browser." All of those look unprofessional and reduce opens.
Letting Body Copy Leak Into the Preview
Headers, navigation bars and logo alt text often become the default preheader. The fix is to add a hidden preheader at the top of your HTML.
Writing Too Much
A long preheader gets cut off. Put the key message early so it survives on mobile.
Being Misleading
A preheader that promises something the email does not deliver may earn an open, but it will also earn an unsubscribe or spam complaint. The goal is more qualified opens, not more opens at any cost.
How to Add a Hidden Preheader
A hidden preheader is the standard way to control preview text without showing it inside the email.
It sits at the very top of your HTML, styled so it is invisible in the body but readable by inbox clients. A typical implementation looks like this:
<div style="display:none;max-height:0;overflow:hidden;mso-hide:all;">
Your preheader text goes here — followed by enough spaces to prevent body copy
from leaking into the preview.
</div>
After your preheader text, add a string of non-breaking spaces or a zero-width non-joiner. This prevents the next line of body copy from appearing after your preview text runs out.
If you want help generating clean preview text, try our email preheader generator or email preheader optimizer.
Preheader Text on Mobile
More than half of emails are opened on mobile, so mobile preview behaviour should drive your decisions.
On a phone, the preheader usually appears as a second line below the subject. That means it is the last thing a subscriber reads before they tap or scroll past. Keep it concise, front-loaded, and easy to understand at a glance.
This also ties into the broader topic of how long someone actually looks at an email. You have seconds, and the preheader is part of the first impression.
Testing and Measuring Preheaders
Treat preheader text as a testable element, just like a subject line.
- A/B test it. Keep the subject line the same and try two different preheaders.
- Track open rate by device. A preheader that wins on desktop may not win on mobile.
- Watch the full preview. Send test emails to several clients and check what actually appears.
- Use a scoring tool. A subject line analyzer or subject line emotion scorer can help you evaluate how the subject and preheader feel together.
Key Takeaways
- Preheader text is the preview copy that appears with your subject line in the inbox.
- It effectively doubles the space you have to earn an open.
- Keep the most important words in the first 40–50 characters and the total under 100 characters.
- Expand on the subject line rather than repeating it.
- Use a hidden preheader to control the preview and stop body copy from leaking in.
- Test preheaders the same way you test subject lines.
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