Free tool
Cold email subject line tester
Paste a subject line and get an instant score with specific fixes: length, spam triggers, capitalisation, punctuation, and personalisation. Free, and it never leaves your browser.
What the tester checks
- Length: 28 to 60 characters reads well across inboxes, including mobile previews.
- Spam triggers: words like free, guarantee, and act now can hurt deliverability.
- Capitalisation: ALL-CAPS words read as shouting and can trip filters.
- Personalisation: a merge variable such as {{first_name}} or {{company_name}} lifts opens.
Frequently asked
What makes a good cold email subject line?
Keep it short (roughly 28 to 60 characters), specific, and personal. Use a merge variable like the company name, avoid spam-trigger words and ALL CAPS, and skip heavy punctuation or emoji for B2B.
Is this subject line tester free?
Yes, completely free and it runs entirely in your browser. Nothing you type is sent anywhere.
Write subjects that get opened, then send them
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