Preheader
The short line of text an inbox shows after the subject line, taken from the start of the email body; senders often set it with a hidden element at the top of the HTML.
What it means
No header field carries it. Mail programs build the preview from the first text in the message, so a sender who does nothing gets whatever comes first, such as View in browser, and Litmus notes that some programs take it from image alt text instead. To control it, senders place the text they want at the very top of the HTML, often hidden in the opened message. Litmus distinguishes preview text, what the inbox shows, from preheader text, a visible line above the email's header, though many people use the two words interchangeably.
How much appears depends on the program and the screen. Google warns against using HTML and CSS to hide content in general, so a hidden preview line should hold genuine text that matches the email.
Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- Litmus: The ultimate guide to preview text supportlitmus.com
- Google, Gmail Help: Email sender guidelinessupport.google.com
All 432 terms in the glossaryThe wiki: blocklists and bounce codes