Free tool
Subject line tester
Score your subject line, see where it gets cut off on mobile, and catch spam triggers and other easy fixes before you send. Free, no sign-up to get your score.
Where subject lines get cut off
Most email is opened on a phone, where you get far fewer characters than on a laptop. These are rough figures: the exact cut-off depends on the screen, the font and the letters you use.
| Where | Characters shown |
|---|---|
| iPhone Mail, portrait | about 35 to 45 |
| Gmail app, phone | about 35 to 45 |
| Outlook, desktop | about 50 to 60 |
| Gmail, desktop | about 60 to 70, including the preheader |
Five habits of subject lines that get opened
- Put the point in the first 40 characters.That's what phone users see. Anything after is a bonus.
- Be specific."Your 3 shortlisted courses" beats "An update from us". Numbers, names and dates all help.
- Write it like a person would.Sentence case, one exclamation mark at most, no shouting in capitals.
- Use the preheader.It's free space next to your subject. Don't leave it showing "View in browser".
- Test, don't guess.Send two versions to a slice of your list and roll out the winner.
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Questions
How is the score worked out?
Your subject line earns points out of 100: plain, recognisable words (25), length (20), looking trustworthy, with no spam phrases, shouting or excess punctuation (20), specific details like numbers, dates and names (15), writing for the reader (10), word count (5) and the preheader (5). We check every word against a dictionary of over 75,000 English words, so typos and random letters are caught. Text we can't read as words scores no more than 15, and spammy subject lines can't score above 49.
Does a high score mean more opens?
No tool can promise that. Your sender name, your list and what you're offering matter more. The score catches the common mistakes, so your subject line isn't what holds you back. A/B testing tells you what actually works for your audience.
Do you store my subject lines?
No. The score is worked out in your browser and nothing is sent to us. If you sign up for tips by email, the address you give is saved with our form provider, Tally, as set out in our privacy notice.
What's a good open rate?
Open rates aren't as reliable as they used to be. Since Apple's Mail Privacy Protection arrived in 2021, Apple Mail can load emails in the background, which counts as an open whether or not anyone reads it. So open rates now look higher than reality, and they vary with how many of your subscribers use Apple Mail.
Use opens to compare your own subject lines against each other, sent to the same list at a similar time. To judge how an email actually performed, look at click rate, replies and what people did after they clicked. And compare against your own past results rather than an industry average, because lists, offers and audiences differ too much for one number to mean much.
What's a preheader?
The grey preview text that shows after your subject line in most inboxes. If you don't set one, email apps grab the first text in your email, which is often "View this email in your browser".