Free Email Subject Line Tester

Score your email subject lines before you hit send. Check character length, emotional impact, spam triggers, and mobile preview fit.

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What makes a great email subject line?

A great email subject line does three things: it gets opened, it sets accurate expectations, and it makes the reader feel something. Our tester scores your subject lines across all these dimensions.

Keep it short for mobile

Most email opens happen on mobile, where subject lines are cut off after 30–40 characters. Our tester tells you exactly whether your subject line will be truncated on mobile.

Avoid spam triggers

Words like "free", "guaranteed", "urgent", and "limited time" can trigger spam filters and reduce deliverability. Our Pro tier checks against 500+ known spam trigger words.

Use emotional and power words

Subject lines with emotional or power words see 10–25% higher open rates. The analyzer identifies and scores these words in your subject line.