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Email Subject Line Tester

Score your subject line on deliverability, open-rate potential, and emotional impact. Get 5 improved variations instantly.

Free. No signup required.

How It Works

Enter a subject line and get a detailed breakdown with actionable improvements.

1

Type your subject line

Enter any email subject line you want to test.

2

Get your score

Scored across 6 dimensions: length, power words, spam risk, emotional appeal, clarity, and preview compatibility.

3

Copy an improved version

Get 5 auto-generated variations with scores — copy the best one.

0 characters0 words

Write Email Subject Lines That Get Opened

Subject Lines Make or Break Your Open Rate

47% of email recipients open emails based on the subject line alone.

  • Optimal length is 35-45 characters for maximum opens across all clients
  • Spam trigger words can land your email in junk even with a clean sender reputation
  • Power words and emotional triggers correlate directly with higher open rates
  • Personalization ("you", "your") increases opens by 26% on average

Test Before You Send

Write 3-5 variations and pick the highest-scoring one before hitting send.

Inbox Preview Matters

Different email clients truncate subject lines at different lengths.

  • iPhone shows only ~35 characters in portrait mode
  • Gmail desktop shows ~70 characters before truncating
  • Front-load your key message in the first 5 words

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