Definition
Email preheader length refers to the number of characters of preview text that appears next to or below a subject line in an inbox, and how much of it is visible before truncation. This text is drawn from the first line of the email or an explicit preheader and acts as a second chance to persuade the recipient to open. Managing its length is essential because inboxes display only a limited window.
How It Works
Email clients pull preview text from the email body, often the first text element or a hidden preheader snippet, and display it alongside the subject line. On desktop, this may show 80 to 120 characters, while mobile screens often show fewer. If the first visible text is a web version link or an image alt tag, that junk text is shown instead, wasting valuable space. Senders therefore control preheader text deliberately.
Length matters because the preheader must deliver its message before it is cut off. A well-sized preheader extends the subject line's promise, adds a benefit, or creates urgency, giving the recipient another reason to open. If it is too short, the opportunity is wasted; if it is too long, the key point may be truncated. Testing across clients helps find the optimal length for a given audience.
Best Practices
- Write a preheader of roughly 40 to 90 characters that survives common truncation.
- Place the most important words at the beginning of the preheader.
- Avoid letting "View in browser" or similar utility text appear first.
- Use the preheader to complement, not repeat, the subject line.
- Preview the preheader in both desktop and mobile inboxes before sending.
Example
A retailer writes the subject line "Your 25% off code is inside." Its preheader reads, "Ends Sunday — plus free shipping over $50." On mobile, the display truncates to "Ends Sunday — plus free shi…," but the deadline still comes through. The concise preheader supports the subject line and gives the recipient a concrete reason to open.
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Frequently Asked Questions
Aim for roughly 40 to 90 characters so the key message fits the inbox preview on most devices, though the exact limit varies by client.
The client will pull the first available text, which may be an irrelevant link or alt text, wasting the preview space and potentially lowering open rate.
It can, but a stronger approach is to add new information, such as a deadline or benefit, to give readers an additional reason to open.