Email Subject Line Tester - Optimize Email Opens

Test email subject lines for length, spam triggers, and best practices. Preview how subjects appear in Gmail and Outlook.

Subject Line

Characters: 0/50 recommended

Preheader Text (optional) Sender Name

Gmail / Mobile

Your subject line appears here

Preheader text shows here...

Outlook Desktop

Your subject line appears here

Enter a subject line to analyze.

Keep it under 50 characters, avoid spam words, use personalization, create urgency, and make it relevant to recipients.

Common spam words like FREE, URGENT, !!!, ALL CAPS, excessive punctuation, and misleading phrases.

41-50 characters is optimal. Mobile shows ~30-40 chars, desktop shows ~60. Test on both.

This is a content analyzer. It checks for spam triggers but can't test actual deliverability.

Emoji can improve open rates when relevant. The tool shows how they render across email clients.

Enter your preheader text to see the full preview as it appears in inbox previews.

Yes. All analysis happens in your browser. No subject lines are saved or sent anywhere.

Test multiple variations before sending. A/B test different approaches with small segments to find what resonates with your audience.

The tool doesn't save history. Copy promising variations to a document for comparison and later A/B testing.

The spam filter checks English words. Non-English subject lines may show fewer warnings, but character limits still apply globally.