Free tool
Email subject line tester
Type a subject line and get a score out of 100, with each point explained. See how it gets cut on mobile and desktop before you send.
Scored as you type, in your browser. Nothing is sent anywhere.
Inbox preview
Type a subject line to score it
Length, spam words, capitals, punctuation, emoji and personalization, scored out of 100.
Quick answer
What this tool checks
Length and truncation. We count characters (emoji count as one) and preview the cut at about 40 characters on mobile and 60 on desktop.
Spam trigger words. The same English and French phrase list as our spam tester, weighted by how strongly filters react.
Shouting and punctuation. ALL CAPS words, !!!, ?! and $$ are classic spam signals and cost points.
Emoji, personalization and numbers. One emoji is fine, three is too many. We also note merge tags like {{first_name}} and concrete numbers.
How to fix common issues
Cut off on mobile
Move the hook to the first 40 characters and let the preview text carry the rest.
Spam words
Replace hype with specifics: “Free” and “Act now” become what the reader actually gets and why it matters today.
Too much emphasis
Use sentence case, one exclamation mark at most, and a single emoji only if it adds meaning.
Fake “Re:” or “Fwd:”
Remove it. Pretending a campaign is a reply erodes trust and gets penalized.
Frequently asked questions
What is a good subject line length?
Around 25 to 50 characters. Mobile inboxes show roughly the first 40, so the most important words should come first.
Do spam words in the subject really matter?
Less than your sender reputation and authentication, but filters weigh the subject heavily. A few hype phrases on a new domain can tip a borderline email into spam.
Should I use emoji in subject lines?
One relevant emoji can help a subject stand out. Several look promotional and render differently across email clients.
Is my subject line sent to a server?
No. Scoring runs entirely in your browser as you type.
Related tools and guides
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