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Email Subject Line Tester
Score and improve your email subject lines
0 charactersGood length for mobile
Overall Score
0
Poor
Analysis
✗Length
0 chars (20-50 ideal)✗Power Words
No power words found✗Personalization
Consider adding "you"✓No Spam Words
No spam triggers✓No ALL CAPS
Good capitalization✗Has Numbers
Try adding a number✗Question or Urgency
Creates curiosity or urgencySuggestions
- 💡Add more context - your subject is too short
- 💡Add a power word like "new", "free", or "exclusive"
- 💡Personalize with "you" or "your"
- 💡Numbers like "5 ways" or "3 tips" increase open rates
Preview
FM
Founder Mode
to me
Your subject line here...
Hey there! Just wanted to follow up on...
High-Performing Examples
Your quick win for today
5 mistakes killing your conversion rate
New: The feature you requested
Question about your account
[Name], you're invited
What is Email Subject Line Tester?
An email subject line tester evaluates your subject line against proven best practices for open rates. It scores factors like length, word choice, personalization, urgency, emotional appeal, and spam trigger words to predict performance before you send.
How to use this calculator
- 1Type or paste your subject line into the input field.
- 2Review the score and the specific factors flagged: length, emotional words, power words, spam triggers.
- 3Read the detailed feedback explaining each deduction or bonus.
- 4Test 3–5 alternative subject lines to identify which performs best before sending.
- 5Use the winning subject line and A/B test it against the second-best option if your list is large enough.
Why this matters for founders
The subject line determines whether your email gets opened or ignored. With average open rates around 20%, the difference between a good and bad subject line can mean 2-3x more people actually reading your message. This directly impacts campaign ROI.
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