Free tool · 10s · no signup

Email subject line tester
scored on four axes.

Paste your subject. AI scores curiosity, clarity, urgency, and spam risk on a 0–10 scale — then writes 5 stronger variants that fix the weakest axis.

Want to ship the winning subject line today?

Pick the strongest variant above, then drop it into your ESP. The tools we'd actually recommend below. Affiliate-tracked.

The default DTC ESP. A/B subject lines, flows, segmentation, and SMS in one platform.

Free → $20/mo and up

Best for: any brand without a real email program yet.

Library of inspirational ad + email creative. Find subject-line patterns your competitors run.

Best for: finding subject-line angles that already work in your niche.

Frontier Visions (free)

After you've fixed your subject lines, render 3 ad creatives that match the winning angle. Free.

Best for: closing the loop email → ads.