Definition
Preheader text, also known as preview text or Johnson box, is the line of text that appears after the subject line in most email clients. It gives recipients a preview of the email content before they open it. In Gmail, it appears as grey text below the subject line. In Apple Mail, it appears to the right of the subject line.
The preheader is typically pulled from the first text content in the email HTML. If no explicit preheader is set, email clients will automatically pull the first visible text they find, which might be "View in browser", "Having trouble viewing?", or navigation links — none of which encourage opens.
How Preheader Text Appears by Email Client
| Email Client | Preheader Display | Character Limit |
|---|---|---|
| Gmail (desktop) | Grey text below subject line | 100-120 characters |
| Gmail (iOS/Android) | Grey text below subject line | 60-80 characters |
| Apple Mail (iOS) | Text next to subject line | 80-100 characters |
| Apple Mail (macOS) | Text next to subject line | 60-80 characters |
| Outlook (desktop) | Text below subject line | 80-100 characters |
| Outlook (iOS/Android) | Text below subject line | 60-80 characters |
| Yahoo Mail | Grey text below subject line | 100-120 characters |
How to Optimise Preheader Text
- Use the preheader as a second subject line: The subject line hooks the reader, and the preheader provides the next layer of information. Together, they should tell a complete story that encourages an open.
- Set it explicitly in the HTML: Place hidden preheader text at the very top of your email HTML, before any other content. Wrap it in a container with
display: noneandmso-hide: allfor Outlook. This ensures the preheader shows exactly what you want. - Keep it within character limits: Aim for 80-100 characters. Text beyond the limit will be truncated with an ellipsis ("..."). The most important information should appear in the first 50 characters.
- Do not repeat the subject line: The preheader should complement the subject line, not repeat it. If your subject line is "Summer Sale Ends Friday", your preheader could be "Save up to 40% on all summer styles — shop now".
- Include a call to action: Use action-oriented language that encourages opening. Words like "discover", "learn", "shop", "claim", and "start" paired with specific benefits perform well in preheader text.
Common Preheader Mistakes
- Leaving it blank or unset: When no preheader is set, email clients pull the first visible text, which is often "View in browser", navigation links, or the copyright notice. This wastes valuable inbox real estate.
- Stuffing with irrelevant keywords: Preheader text should be meaningful content, not keyword-stuffed SEO fodder. Irrelevant text frustrates recipients and can hurt trust when the email content does not match the preview.
- Making it too long: Long preheader text gets truncated, and the truncation often cuts off the most important part of the message. Always front-load the key information in the first 50 characters.
- Forgetting Outlook: Outlook uses
mso-hide: allto hide elements. If you usedisplay: noneto hide the preheader container, it will still show in Outlook. Always include themso-hide: allCSS property.
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
AMP for Email
AMP for Email is a Google-developed framework that allows email messages to include interactive elements like forms, carousels, accordions, and live content. It turns static emails into dynamic, interactive experiences directly inside the inbox.
CAN-SPAM Act
The CAN-SPAM Act is a US law that sets rules for commercial email. It requires accurate subject lines, a physical address, a clear opt-out mechanism, and prompt processing of unsubscribes. Violations can result in penalties up to $51,744 per email.
Click-Through Rate
Click-through rate (CTR) is the percentage of email recipients who clicked one or more links in your email campaign. It measures how compelling your content and call-to-action are.
Click-to-Convert Rate
Click-to-convert rate measures the percentage of email clicks that result in a desired conversion action such as a purchase, signup, or download. It shows how effective your post-click experience is at turning interest into results.
Frequently Asked Questions
Yes. Well-written preheader text can improve open rates by 5-15% according to industry studies. The preheader gives recipients additional context that helps them decide whether to open your email. It is one of the highest-impact optimisations because it requires minimal effort but affects every recipient who sees your email in the inbox.
The optimal length is 80-100 characters for most email clients. However, because different clients display different amounts, the first 50 characters should contain the most critical information. Place the call to action or key value proposition early in the text.
Place a `
No. Hidden preheader text is a standard and widely accepted email development practice. Major senders and ESPs use it. However, do not hide keyword-dense or deceptive text, as this could trigger spam filters. The hidden text should be a genuine preview of your email content.
The email client automatically pulls the first visible text from your email HTML. This is often the "View in browser" link, a header image's alt text, or navigation links like "Shop Women, Shop Men, Shop Kids". These generic snippets do not encourage opens and waste the opportunity to provide compelling preview content.
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