Definition
Preview text, also known as preheader text, is the line of text shown alongside the subject line in the inbox. On most email clients it is drawn from the first text in the email body unless a hidden preheader is set explicitly. Alongside the subject and sender name, it forms the three-element preview that determines whether an email gets opened.
In 2026, preview text has a second job: it feeds AI inbox summaries. Gmail's Gemini and other AI assistants draw on the preheader and opening lines to generate the summary a subscriber sees. A meaningful preheader now influences both the human decision to open and the machine-generated summary.
Best Practices for Preview Text
- Keep it under 85 characters so it isn't truncated on mobile.
- Never repeat the subject line — use the space to add value.
- End with a hook — "...and your exclusive code inside" pulls readers in.
- Set it explicitly with a hidden preheader div so clients don't pull random body text.
Preview Text Length Benchmarks
| Email Client | Visible Preview Length |
|---|---|
| Gmail (desktop) | ~100 characters |
| Gmail (mobile) | ~35-45 characters |
| Apple Mail | ~85 characters |
| Outlook | ~35-50 characters |
Related Terms
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.
Above the Fold in Email
Above the fold in email refers to the content visible to a recipient before they scroll, a critical area for first impressions and primary calls to action.
Accessible CTA (Email)
An accessible CTA is a button or link coded with sufficient colour contrast, visible focus states, descriptive screen-reader text, and a minimum touch target of 44×44 pixels.
Adaptive Design
Adaptive design in email uses predefined layouts that adjust to specific device or client widths, rather than fluidly resizing to every possible screen.
AI Content Detection
AI content detection refers to the growing ability of email clients, spam filters and consumers to identify machine-generated email copy. It matters for deliverability, trust and engagement in an era of mass-produced AI marketing email.
Frequently Asked Questions
The subject line is the primary headline; preview text is the supporting line that appears beside it. Together they form the two-line hook that earns the open.
Add a hidden table cell or div with the preview text at the top of the email body, styled to be invisible (e.g. display:none with an Outlook-safe fallback), so clients display it instead of random body copy.
No, but it directly affects open rate, and in AI inboxes it influences the generated summary that determines whether the email gets attention at all.