Email preheader
The line of text displayed just after the subject line in the inbox preview, before the message is opened by the recipient.
Without a defined preheader, email clients show the beginning of the message body — often 'Hello {{first_name}}' or 'View in browser', which gives no reason to open.
It is a second chance after the subject line: it complements rather than repeats. If the subject asks a question, the preheader hints at the answer.
How many characters are shown depends on the email client and screen size; around a hundred is the safe estimate to write to.
In Mailcheer, it is a field next to the subject line. It accepts up to 200 characters and supports personalization variables like the rest of the message. It does not appear in the message body: only the inbox displays it. The writing assistant suggests a preheader at the same time as the subject line, never the subject line alone.
Why it matters
The subject line and the preheader together form everything a reader sees before deciding to open. Neglecting the second means giving up half your storefront.