Subject Line Tester
Score an email subject.
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About Subject Line Tester
Test any email subject line as you type and get an instant score out of 100. This free tool checks character length against the 30-50 sweet spot, warns when a line is too long for mobile inbox previews, and counts words and emoji. It also flags ALL-CAPS shouting, excessive punctuation, common spam-trigger words, and whether you have added personalization.
Every check runs live in your browser with no sign-up and no limits. Nothing you type is ever uploaded or saved, so you can paste real campaign subjects freely. Use the concrete tips to tighten each line before you hit send.
Frequently asked questions
- Is the email subject line tester free?
- Yes, it is completely free with no account, sign-up, or usage limits. Test as many subject lines as you like.
- Is my data uploaded or stored anywhere?
- No. The entire analysis runs in your browser using JavaScript. Your subject lines are never sent to a server, uploaded, or stored, so it is safe to paste real campaign copy.
- What is the ideal email subject line length?
- Aim for roughly 30-50 characters. That range stays fully visible in most inboxes and, importantly, in mobile previews that often cut off anything past about 30-40 characters. Longer lines up to 60 characters usually still work, but the end may be clipped on phones.
- How is the score out of 100 calculated?
- The tool starts at 100 and adjusts based on best practices: it deducts points for lines that are too long or too short, ALL-CAPS shouting, excessive punctuation, detected spam-trigger words, and emoji overload, and it adds points for personalization such as a merge tag or addressing the reader directly.
- Which spam-trigger words does it detect?
- It checks against an inline list of common ones like 'free', 'buy now', 'guarantee', 'act now', 'click here', 'winner', '100% free', and symbol patterns like '$$$'. Any matches are listed inline so you can rephrase them. Avoiding these reduces the chance of landing in the spam folder.
- Does a high score guarantee my email gets opened?
- No. The score reflects widely used deliverability and readability best practices, but open rates depend on your sender reputation, audience, timing, and preview text too. Treat the score as a guide and always A/B test real subject lines with your own list.