Score subject lines for open rate potential. Detect spam words, preview mobile/desktop truncation.
Type subject lines on the left to instantly score open rate potential and see inbox previews.
The Email Subject Tester scores your subject lines across 7 key open-rate factors: length, spam word risk, curiosity gap, personalization, urgency, numbers, and emoji. It also simulates how your subject appears in a mobile inbox (~40 chars), desktop client (~60 chars), and Gmail (~77 chars) — so you can see exactly what subscribers read before deciding to open.
Industry data consistently shows 28–50 characters drives the highest engagement. Mobile email clients truncate at ~40 characters, so the most critical words should appear first. Avoid writing long subjects hoping the preview text will save it.
Yes, but modern spam filters are more sophisticated than a simple word list. High-risk words like "FREE!!!" or "BUY NOW" combined with other signals (sender reputation, link count) dramatically increase spam folder placement. Avoiding them is always safer.