How does the subject A/B battle work?

Each subject is scored on seven factors: length, ALL CAPS ratio, exclamation count, emoji density, urgency wordlist match, personalisation tokens, and whether it leads with an action verb. The factors are weighted (verb 25%, length 18%, personalisation 15%, the rest 10-12%) and combined into a single 0-100 score. The higher score wins.

Is it niche-calibrated?

The scoring weights stay the same across niches; the optimal length and emoji budget vary slightly. Pick your niche from the dropdown and the verdict line factors that in.

Why did Subject A win when it looks worse?

Look at the per-factor breakdown - usually the loser has 3+ exclamation marks, ALL CAPS over 30%, or starts with a weak verb like Click or Submit. Those penalties dominate the total.

Yes. The battle runs entirely in your browser, no signup, no rate limits.

⚔️ Free A/B test

Subject line A/B battle

Paste two subjects. See who wins, by how much, and exactly why - on seven scoring factors, in your browser.

0-100 head-to-head 7 factors No signup

FAQ

Frequently asked questions

How is the score calculated?

Seven factors: length (18%), ALL CAPS (12%), exclamations (10%), emoji (10%), urgency words (10%), personalisation (15%), and action-verb start (25%).

Can I share the result?

Copy the URL after a battle - your subjects are encoded in the hash so the link reproduces the result anywhere.

Why did the verbose one win?

Length matters but verb strength weighs 2.5x as much. "Save 30 minutes today" beats "Hi" because the verb does the heavy lifting.

Free?

Yes - all client-side. No signup, no rate limits.

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