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Email Subject Line Tester

Your subject line decides whether the email you spent an hour writing gets opened or archived in one second. Paste a subject line and get a 0–100 score across the factors that actually move open rates — with specific, actionable fixes for what's dragging yours down.

Scored on length, spam triggers, caps, punctuation, emoji and personalization.
Subject line score—Enter a subject line to see its score.

How it works

The tester scores your subject line on evidence-based heuristics: length (30–50 characters is the sweet spot — long enough to be specific, short enough for mobile), spam trigger words ('free!!!', 'guarantee', 'act now' hurt deliverability), ALL-CAPS abuse, repeated punctuation (!!, ??), emoji count (one can help, three look like spam), presence of a number (specificity lifts opens), and personalization tokens.

Each factor shows its contribution to the score plus a one-line fix. The goal isn't a perfect 100 — it's catching the two or three issues that silently cap your open rate.

FAQ

Roughly 30–50 characters. Mobile clients truncate around 35–45, so front-load the interesting part. Ultra-short lines (1–3 words) can work for curiosity, but only when your sender name already carries trust.

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