What a preheader is for
The preheader — also called preview text — is the snippet that appears right after your subject line in the inbox. It's a second headline, and most senders waste it: they either leave it blank (so the client grabs a stray link or alt tag) or they repeat the subject. Done well, the subject and preheader work as a one-two punch that lifts opens without changing a word of the email itself.
The rules that hold up
- Complement, don't repeat. The subject and preheader show together, so echoing the subject burns the space. Add a new hook, a detail, or a reason to open.
- Length: about 40–100 characters. The first 40–50 show on mobile; desktop displays up to ~100–140. Front-load the point.
- Always set one. Never leave it to chance — an empty preheader means the client picks the text for you, usually badly.
- Match the tone. It reads as one line with the subject, so keep the voice consistent.
Frequently asked questions
How long should an email preheader be?
Roughly 40–100 characters. The first 40–50 show on mobile; desktop shows up to ~100–140. Front-load the hook.
Should the preheader repeat the subject line?
No — they appear together, so repetition wastes space. Add something new.
What happens if I don't set a preheader?
The client grabs the first readable text, often a link or alt tag. Set a dedicated preheader to control it.
See it across every client with the inbox preview, or run everything through the pre-send checker.