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The #1 FREE subject line rating tool that allows marketers to test any subject line for possible deliverability and marketability issues. Provides marketing-related suggestions based on results that can improve overall open rates on emails sent. Results from this tool are based on 3 billion+ email messages that have been sent and tracked via SubjectLine.com's partners and clients.

What’s New

Version 3.56

· SubjectLine.com App now applies over 900+ unique rules
· Updated rules to reflect the latest marketing research trends
· Performance results based on 'Marketability' and 'Deliverability'
· Over 4 Million Subject Lines checked via the SubjectLine.com tool
· New features include advanced checks on forms of Urgency and Exclusivity.
· SubjectLine.com is now an Ad Supported site - Included are an ESP and Data Hygiene Marketplace

Ratings and Reviews

4.6 out of 5
5 Ratings

5 Ratings

Cameronhayden ,

Great app for email marketing

I have used this app many times to help with my client's email needs. This app has been extremely helpful tool. Highly recommend it for any email marketer

Mktgdir ,

Great app for marketers

When planning my company's email programs, deciding on subject lines to test is one of our most popular discussions. With this subject line app I easily paste a few ideas in and it helped us quickly decide which ones had the most potential. It's a great recourse for anyone doing corporate marketing!

nchalkias ,

Very useful

I found this useful in order to check the email's subject line before sending it. Nice to see what the recommendations come out to be.


Worldata InfoCenter, Inc.
60.2 MB

Requires iOS 7.0 or later. Compatible with iPhone, iPad, and iPod touch.


English, Italian, Portuguese, Russian

Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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