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Subject line preview

/subject

See how your subject and preview text cut off on phones and desktops.

Why subject length matters

  1. What it is

    Every inbox truncates the subject line at a different width — and phones show the least.

  2. Why it matters

    Front-loading the important words means your message reads correctly everywhere.

  3. Without it

    Write too long and the point gets cut off exactly where it matters most.

What we show

  • How your subject truncates on iPhone Mail, Gmail app, Gmail desktop, Outlook and Apple Mail
  • The character count, with guidance on the sweet spot
  • How the preview text reads alongside the subject

Common questions

What subject length works best?

Aim for roughly 30–50 characters. Mobile clients show the least — often under 40 — so front-load the important words.

Does preview text matter?

Yes. It's the grey line after the subject in most inboxes. A good preview extends the subject rather than repeating it.