// email optimization
Email Subject Line Tester
Score your email subject line from 0 to 100. Get detailed analysis on length, spam triggers, personalization, urgency, and more.
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// how it works
How to use Subject Line Tester
- 01
Type your subject
Enter the email subject line you want to test. The tool accepts any length and format including emojis and personalization tokens.
- 02
Get your score
Receive an instant score from 0 to 100 with a letter grade based on eight key factors that affect deliverability and engagement.
- 03
Improve & retest
Review detailed feedback on each factor, make improvements, and test again until you reach a high score.
// features
Why use Subject Line Tester
Spam detection
Scans for over 35 known spam trigger words that can land your email in the junk folder.
Length check
Verifies your subject line falls within the ideal 30-50 character range for maximum visibility.
Power words
Detects urgency words and action triggers that motivate recipients to open your email.
Emoji analysis
Evaluates emoji usage and warns when they may help engagement or trigger spam filters.
Character count
Shows exact character count so you can optimize for mobile and desktop email clients.
Privacy first
All analysis runs locally in your browser. Your subject lines are never stored or transmitted.
// use cases
Who uses Subject Line Tester
Email marketers
Score and optimize campaign subject lines before sending to maximize open rates across your list.
Sales teams
Test cold outreach subject lines to avoid spam filters and increase reply rates from prospects.
Newsletter editors
Validate newsletter subject lines to maintain consistent engagement with your subscriber base.
Campaign managers
Compare multiple subject line options by score to choose the strongest performer for each send.