Free Email Subject Line Analyzer

How this tool computes its result

Scores a subject line out of 100 using additive/subtractive rules: length in the 30-50 character band (+30, the best band), word count in the 3-7 word band (+20), a personalization keyword match like 'you'/'your'/'name'/'company' (+15), an urgency keyword match like 'now'/'today'/'urgent'/'limited' (+10), presence of any digit (+10), presence of an emoji via a Unicode range regex (+5, alongside a caution note), and a question mark (+5). It then subtracts points for spam-trigger keywords (free, click here, buy now, guaranteed, winner, '$$$', etc. — each -5), ALL CAPS text (-10), and more than one exclamation mark (-5). The score is clamped to 0-100 and mapped to a letter grade: A >= 80, B >= 65, C >= 50, D >= 35, else F.

Worked example

Subject line 'Your 5 tips to boost sales today!' — length 34 chars (30-50 band, +30), 7 words (3-7 band, +20), contains 'your' (personalization, +15), contains 'today' (urgency, +10), contains a digit '5' (+10), a single '!' (no penalty, needs more than one to trigger). No spam words and not all caps. Total score lands around 85, earning a grade of A.

When not to use this tool

This is a static, offline heuristic — it does not check the subject line against a live inbox placement test, an ISP's actual spam filter, or historical open-rate data for a specific audience, so a high score here is directional, not a deliverability guarantee.

Common mistakes

• - Assuming any emoji use is penalized — the analyzer actually adds +5 to the score for an emoji while also surfacing a caution recommendation about spam filters, which can read as contradictory at a glance.
• - Writing a subject line in ALL CAPS for emphasis — this triggers a flat -10 penalty and is listed as a spam trigger regardless of brand voice or intent.
• - Stacking multiple exclamation marks for enthusiasm — more than one '!' is penalized -5 and flagged as a spam trigger, even when none of the surrounding words are spammy on their own.

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