Subject Line Scorer.free tool

Free tool · no sign-in

Your subject line gets one second to earn the open.

Paste the line you were about to send, and the preheader beside it. You get a score out of 100, the reason behind every point, the inbox row as it lands on phone and desktop, and five rewrites in whichever angle you pick.

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Or try one

How the score is built

One hundred points across five bands, weighted the way inboxes actually behave.

  • Length, 20 points. 30 to 50 characters fits desktop and mobile without truncating.
  • Trigger words, 30 points. Ten angles, from curiosity to authority. Two beats one; three is usually noise.
  • Power words, 15 points. One well-placed word lifts a line. Four make it read like an advert.
  • Spam safety, 20 points. Thirty-three phrases filters react to, plus shouting and stacked exclamation marks.
  • Reader focus, 15 points. Whether the line speaks to one person or broadcasts at a list.

The preheader is judged separately, not folded into the hundred, because it does a different job: the subject earns the glance, the preheader earns the open. It is checked for length, for repeating the subject instead of extending it, for spam phrasing, and for the boilerplate a client drops in when you leave it blank.

Nothing you type is sent anywhere. The whole tool runs in this browser tab.

If you promote other people's launches

Scoring one line at a time is the slow way.

BonusPlane takes the launch page URL and your affiliate link, builds the bonus page and the delivery page, and now writes the promo emails that send your list there. Every subject line in that series is scored by this same engine before you see it, and anything that would land in spam is held back with the reason.

See BonusPlane

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