Free Email Subject Line Checker
Score your subject line as you type. Catch length problems, shouting capitals, spam words and emoji overload before they cost you opens.
Live analysis runs in your browser — nothing is uploaded.
Inbox previews
Mobile
Mailvern
Your subject line appears here
Hi Sarah, here is the summary you asked for…
Desktop
Start typing to see your score
The score, issues and improvement tips update instantly with every keystroke.
Your subject line decides whether the rest of the email exists
It is the only part of your message most people ever read. These are the factors that move open rates.
Most email is read on a phone
Mobile inboxes cut subject lines around 35–45 characters. If your value is at the end of a 90-character sentence, nobody sees it. Front-load the specific thing the reader cares about and let the preview text carry the rest.
Specific beats clever
"Invoice #1042 is due Friday" outperforms "An important update for you" because it tells the reader exactly what happens if they ignore it. Clarity is the highest-converting style in business email.
Filters read the subject first
Shouting capitals, stacked exclamation marks, currency amounts and words like free, winner or act now all add points to a spam score before the body is even parsed. A calm subject keeps you out of that lane.
How to use this checker
Type or paste your subject line, watch the score update live, then work down the suggested improvements until the meter is green. Check the mobile preview to confirm the important words survive truncation, then copy it into Gmail or Mailvern.
Example usage: rewriting a weak subject
Start with "URGENT!!! FREE consultation available NOW" — it scores in the high-risk band for capitals, repeated punctuation and two trigger words. Rewrite it as "15 minutes to review your Q3 shipping costs?" and the score jumps into the excellent band: natural case, one idea, a specific benefit and 45 characters that survive mobile truncation.
Good vs bad subject lines
Four rewrites you can copy the pattern from.
Invoice #1042 is due Friday
URGENT!! YOUR PAYMENT IS OVERDUE!!!
Specific and calm beats shouting. Capitals and stacked punctuation are classic filter triggers.
Quick question about your Q3 hiring plan
FREE consultation — act now, limited time!
A real question invites a reply. Promotional urgency reads as bulk marketing.
Your March report is ready, Sarah
🎉🎉 AMAZING NEWS INSIDE 🎉🎉
Personalization and clarity outperform emoji spam every time.
3 changes to your delivery schedule
You won't BELIEVE what we changed
Numbers set expectations; clickbait erodes trust and open rates over time.
Frequently asked questions
Everything people usually ask about this tool.
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