Free Email Subject Line Tester
Runs locallyUpdated October 25, 2026
Free email subject line tester: check character length for mobile inbox truncation, spot ALL-CAPS formatting, and flag common spam trigger words before sending.
34 characters
- No obvious spam-pattern hits from our small dictionary.
How to use Email Subject Line Tester
Paste or type your draft email subject line into the tester.
Check the live character count (aim for under 50–70 characters so mobile inboxes do not cut off your hook).
Review any warnings for ALL-CAPS styling or common spam-trigger phrases, then A/B test your top two options in your email platform.
Test your email subject line before hitting send
This free email subject line tester checks your draft subject line in real time right in your browser. It counts characters, warns you when a line exceeds 70 characters (where mobile and desktop clients routinely truncate text), flags ALL-CAPS shouting, and checks against common promotional spam phrases.
Email subject line length & formatting checklist
| Check | Target Guideline | Why It Matters |
|---|---|---|
| Mobile visibility | 30 to 50 characters | Ensures the entire hook is visible on iPhone and Android inbox screens |
| Desktop cutoff | Under 70 characters | Prevents awkward mid-word ellipses (...) in webmail layouts |
| Capitalization | Sentence case or Title Case | Reads naturally and avoids spam-filter suspicion triggered by ALL CAPS |
| Promotional triggers | Specific value over hype | Phrases like 100%, act now, or free money erode reader trust |
Concrete subject line examples (weak vs. strong)
- Too vague & hype-heavy:
ACT NOW: 100% Guaranteed Marketing Secret Inside!(50 chars — triggers spam warnings and tells the reader nothing specific) - Too long (truncates on mobile):
Our Brand New Monthly Product Update Newsletter With 5 Useful SEO Checklists for Your Team(90 chars — cuts off before the value appears) - Clear & specific:
May SEO checklist: 5 meta tag fixes that take 10 minutes(56 chars — front-loads the topic and concrete takeaway)
Related marketing & headline tools
Want to score your wording for power words or blog titles? Try the headline analyzer, generate button copy for your email body with the CTA button text generator, or build campaign tracking links for your newsletter with the UTM builder.
Email Subject Line Tester FAQs
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