Paste your subject line and preview text. Get an instant score on openness, tone, length, and spam risk — with specific suggestions to improve.
Instant analysis — everything runs in your browser.
Subject Line Score
Overall Rating:
Once your subject is optimized, Taildove's campaign analytics show you exactly who opened, clicked, and converted — so you keep improving.
Four factors consistently separate subject lines that get opened from those that get ignored or filtered.
Length
30–50 characters is the sweet spot — long enough to convey value, short enough to display fully on mobile. Subject lines under 15 characters feel vague; over 70 get clipped in most clients.
Spam triggers
Words like FREE, GUARANTEED, and ACT NOW train spam filters to deprioritize your email. They also reduce trust with readers. Specificity always outperforms hype.
Urgency words
One or two urgency cues (deadline, ending soon, new) give readers a reason to open now rather than later. Zero urgency feels passive; too many reads as desperate.
Preview text
The preview text is your subject line's wingman. 40–90 characters that extend the story — not repeat it — can meaningfully lift open rates. Empty preview text wastes valuable real estate.
Is this free?
Yes — completely free, no account required. All analysis runs entirely in your browser. We don't store your subject lines or any other data.
What spam words do you check?
Common trigger words that spam filters and readers respond negatively to, including FREE, URGENT, GUARANTEED, WINNER, CASH, PRIZE, CLICK HERE, ACT NOW, LIMITED TIME, MAKE MONEY, WORK FROM HOME, BUY NOW, SPECIAL OFFER, and more. Using even one of these adds risk; multiple compounds it.
What's the ideal subject line length?
30–50 characters (roughly 6–10 words) is the consistently recommended range. This displays fully in most email clients and inbox previews, including mobile. At 60+ characters you risk clipping; under 20 you risk appearing vague.
Does preview text really matter?
Yes — significantly. Most email clients display 40–90 characters of preview text next to the subject line. A well-written preview that extends (not repeats) your subject can lift open rates by 10–20%. Leaving it empty lets your email client pull random copy from the email body, which often looks broken or spammy.
