Why the inbox preview matters
Before anyone reads a word of your email, they judge three things in the inbox: who it's from, the subject line, and the preheader. Together they decide whether the email gets opened or ignored. The catch is that every email client truncates them differently — a subject that reads perfectly on desktop can be cut mid-word on a phone, where most people actually open email.
Roughly where each client cuts off
- Mobile (iPhone Mail, Gmail app) — about the first 33–41 characters of the subject, then a line or two of preheader.
- Gmail desktop — around 70 characters of subject, with the preheader trailing on the same line.
- Outlook desktop — around 73 characters, preheader on the next line.
- Apple Mail — the full subject plus up to two lines of preheader.
Get the preheader right
If you don't set a preheader, clients pull the first readable text from your email — often an image alt tag or a "View in browser" link. That's wasted inbox space. Write a dedicated preheader that adds a second reason to open, rather than echoing the subject. The two should work as a pair.
Frequently asked questions
How many characters of a subject line show in the inbox?
Mobile shows roughly 33–41, Gmail desktop about 70, Outlook about 73, and Apple Mail the full subject with two lines of preheader. Front-load the important words.
What is preheader text?
The preview snippet shown after the subject. It's taken from the first visible text unless you set a dedicated preheader.
Why does my preview show unexpected text?
Without a set preheader, clients grab the first readable text — often a link or alt tag. Set an explicit preheader to control it.
Want the subject scored too? Try the subject line tester, or run the whole email through the pre-send checker.