Email subject line checker
Type a subject and preheader and see them in iPhone Mail and Gmail, where phones cut them, and what makes them read like a pitch. It checks as you type, in your browser.
How to read the result
The previews cut the text by width, like the real apps, but fonts and screens differ, so treat them as close, not exact. What matters is that the first 35 or so characters carry the meaning.
Problem is for things that mislead people, like a fake Re:. Needs attention is for shouting, piles of punctuation or emoji, and a subject cut on every screen. Phrases like “act now” are mentioned as a hint only: on their own they rarely decide anything, but people skim past them.
Whether mail reaches the inbox depends far more on the domain it comes from. Check that with the domain health check.
Questions
- How long should an email subject line be?
- Phones in portrait show about 35 characters, desktop Gmail about 70 with the preheader after it. Aim for 30 to 50 characters with the important words first. For product email, clarity beats brevity: “Your invoice for March is ready” is better than “Invoice”.
- Why is there no spam score?
- Because a subject line alone does not decide where an email lands. Gmail and Outlook judge the sender's reputation, SPF, DKIM and DMARC, and how recipients treat earlier mail. A word like “free” in a receipt from a trusted domain is fine; a perfect subject from a new domain without DMARC is not. A score would suggest otherwise, so this tool points out patterns instead.
- What is a preheader?
- The short preview text clients show after the subject. If you do not set one, they take the first text of the email, often “View in browser” or an image's alt text. Set it to continue the subject: a date, an amount, the next step.
- Is my subject line sent anywhere?
- No. The checks run in your browser as you type. The subject and preheader are put in the page address so you can share a link to them; nothing is sent to a server.
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