SubjectLine.com
Email subject line rating tool and AI copy optimization assistant
pricingfree tierapichecked 22 Aug 2026
What SubjectLine.com is
SubjectLine Pro scores email subject lines against an extensive database of over 6 billion evaluated email campaigns. It tests for spam trigger words, optimal character length, emotional urgency, personalization tokens, and emoji usage, providing actionable recommendations to boost email deliverability and recipient engagement rates before sending marketing broadcasts.
Pricing
| Plan | Price | Annual | What you get |
|---|---|---|---|
| Free Tester | Free | — | Single subject line scores, basic spam detection, character count checks |
| Pro Marketer | $29/mo | $19/mo | Unlimited subject line checks, AI rewrite suggestions, competitor comparisons |
| Agency | $89/mo | $69/mo | Multi-user seats, bulk CSV testing, white-label client PDF exports |
Includes AI-driven alternative subject line generator.
Free access: Free single subject line checker available on web
read from the vendor pricing page · 22 Aug 2026 · how we verify
Best for
- Email marketers wanting instant copy scoring before sending
- Copywriters testing spam score risks on newsletter headlines
Not for
- Full CRM marketing automation workflows
Integrations
SubjectLine.com alternatives
All 5 alternatives to SubjectLine.com, compared Get the Toolvern badge for SubjectLine.com
Headline Studio by CoSchedule AI headline and subject line analyzer scoring engagement potential 
SendCheckIt 16-point email subject line tester and deliverability grader 
Phrasee AI subject line optimization and language generation for enterprise email marketing 
TestSubject Mobile email subject line and sender name preview simulator 
Touchstone Predictive email subject line testing and open rate simulation engine Head to head: SubjectLine.com vs Headline Studio by CoSchedule SubjectLine.com vs SendCheckIt SubjectLine.com vs Phrasee SubjectLine.com vs TestSubject SubjectLine.com vs Touchstone
Compiled by Stepan Noianov from the vendor's own site and pricing page. Something wrong? Report an inaccuracy.