Email Subject Line Tester
Score email subject lines for open rate potential. Checks length, spam triggers, and urgency markers.
What is Email Subject Line Tester?
Email subject lines determine open rate. Best practices: 30-50 characters (fits mobile), avoid spam triggers (FREE, !!!, ALL CAPS), include personalization markers, create curiosity without clickbait. This tool scores against these patterns.
Frequently asked questions
What's the ideal subject line length?▼
30-50 characters fits both desktop and mobile previews. Longer subjects get truncated; shorter ones can underperform.
What words trigger spam filters?▼
FREE, GUARANTEED, ACT NOW, $$$, all caps, excessive punctuation. Modern filters are smarter but old triggers still hurt.
Related tools
Word & Character Counter
Count words, characters, sentences, paragraphs.
Reading Time Calculator
Estimate reading time for any text.
Headline Analyzer
Score headlines for engagement and SEO.
Markdown to HTML
Convert Markdown to HTML.
HTML to Markdown
Convert HTML to clean Markdown.
Twitter Character Counter
Count characters for Twitter/X posts.