Email Subject Line Scorer
Score subject lines on spam triggers, length, and engagement signals
Try these next
Why use Email Subject Line Tester
- Catches spam-trigger words before a campaign sends, preventing deliverability problems that waste an entire send.
- Mobile preview reveals truncation issues that desktop-only testing misses.
- Side-by-side comparison lets you A/B test variations before committing.
How it works
Seven checks run against a base score of 100. Character count is measured against the 30-60 range. Mobile preview checks whether the text fits ~40 characters. A spam-trigger scan penalizes more heavily when multiple triggers stack. Uppercase ratio flags subjects over 40% caps. Punctuation analysis catches repeated exclamation marks. Engagement detection looks for personalisation tokens, numbers, emojis, urgency, and questions. Word count checks the 6-10 word sweet spot. Each check adds or subtracts, clamped to 0-100, mapped to A+ through F.
About this tool
Type your subject line and get a score from 0 to 100 before you send. The scorer checks seven factors: character count (30-60 is the sweet spot for open rates), mobile preview truncation (~40 characters on phone lock screens), spam-trigger words from a 35+ word database that Gmail, Outlook, and Yahoo flag, capitalization ratio, excessive punctuation, engagement boosters (personalisation tokens, numbers, emojis, urgency cues, questions), and word count (6-10 words performs best). A live mobile inbox preview shows exactly where your subject gets cut off. The feedback is specific -- you see which spam words triggered, how many characters past the preview window you are, and which engagement signals were detected. Compare two variations side by side, pick the higher scorer, and send. The gap between a 45 and a 75 often maps to double-digit improvements in open rate.
How to use Email Subject Line Tester
- Type your subject line. Enter or paste your email subject. Scoring begins as you type.
- Read the score and grade. A 0-100 score and letter grade appear above the detailed breakdown.
- Review each check. Length, mobile preview, spam triggers, caps, punctuation, engagement -- see what passed and what needs attention.
- Check the mobile preview. A simulated inbox row shows where your subject gets truncated on a phone screen.
- Refine and retest. Edit based on feedback. The score updates live. Iterate until you are satisfied.
Use cases
- Testing three Black Friday subject variations to find the one with the highest score and zero spam triggers.
- Verifying cold outreach subjects fit within mobile preview width and include at least one engagement signal.
- Catching a spam-trigger word in a weekly newsletter draft before it tanks Gmail deliverability.
- Scoring a re-engagement campaign subject line that targets lapsed subscribers.
- Comparing an emoji-heavy version against a plain-text version for a product launch announcement.
- Confirming that a personalization token keeps the subject under 40 characters on mobile after the name expands.
Frequently Asked Questions
30-60 characters gets the highest open rates. Under 30 can lack context. Over 60 gets truncated on most desktop clients, and mobile shows even less -- typically 35-40 characters on a lock screen.
Common triggers: 'free', 'buy now', 'act now', 'winner', 'congratulations', 'guaranteed', 'no obligation', 'click here', '100%', 'earn money'. One used sparingly is fine. Stacking multiple triggers in a single subject dramatically increases the odds of landing in junk.
Keep the subject under 60 characters, include a personalisation token like the recipient's name, add a number for specificity, ask a question to spark curiosity, and avoid spam-trigger words. Test send times, segment your audience, and make sure the preview text (preheader) complements the subject rather than repeating it.
Yes. ALL CAPS is one of the strongest spam signals for Gmail, Outlook, and Yahoo. Capitalize a single word for emphasis if you must, but never the entire subject.
One or two relevant emojis can help your email stand out in a crowded inbox. Overusing them looks unprofessional. Emoji rendering varies across clients, so stick to widely supported ones like checkmarks or arrows.
6-10 words tends to perform best. Fewer than 3 lacks context. More than 12 gets truncated and dilutes the message.
About 35-40 characters on a lock screen notification, 30-35 in the inbox list. Front-load your hook so readers see it even on the smallest screen.
Related Tools
Discover more free utilities to enhance your productivity.
Word Counter
Check word count, reading time, and character stats as you type
Character Counter
Track character count against Twitter/X, SMS, and custom limits
Readability Checker
Analyze text readability with Flesch-Kincaid, Gunning Fog, and Coleman-Liau scores
Meta Tag Generator
Generate title, description, Open Graph, and Twitter Card tags from one form