Over 15 million subject lines tested. The #1 free subject line rating tool.

Results from this tool are based on 3 billion+ email messages that have been sent and tracked via SubjectLine.com's partners and clients. Over 800 unique rules are tested that evaluate filtering and deliverability issues as well as marketing and performance related concerns.

This tool gives marketers a better understanding of what will generate increased response rates and improved inbox deliverability. The results you receive should be used as future testing options. Many variables exist in any campaign and subject line that can impact performance well beyond the results of this tool. This tool does not guarantee improved performance and should solely be used as a guide for future testing ideas.

SubjectLine.com is a service of Worldata. Worldata has been the industry leading direct response media agency for over 40 years.