Get Real Subject Line
Test Results Instantly


What is Subject Line Pro?

Subject Line Pro is a virtual subject line test that delivers real accurate results in seconds.

How Does It Work?

With Subject Line Pro, you can create a virtual simulation of your subscriber base to predict likely open, click and delivery rates for any given subject line.

Are The Results Reliable?

Subject Line Pro's proprietary algorithm quickly predicts subjectline performance within 1-2% of actual click rates.

Upload Your Data

Simply sign up and upload your historical campaign data to begin testing.

Start Testing

Enter up to 10 subject lines you're considering using to get the open, click, and delivery rate results instantly.

Compare Your Results

Test your own subject lines against your own data set, as well as our database of 502 billion subject lines across different sectors.

"To get a 20% lift in your click rate, you should test at least 3 subject lines on every single campaign."

source: Zen & the Art Of Subject Line Testing

Create Your Account

    With your account you'll receive:

      Unlimited access to Subject Line Pro's database of billions of subject lines

      Ability to test up to 10 subject lines at once and get results instantly

      Virtual simulation of your own data

      Ability to test by industry

      Technical support

[free until December 31, 2024]


Live A/B Test vs. Subject Line Pro Virtual A/B Test

LIVE A/B SPLIT TEST Subject Line Pro
Sample Size Usually < 10% of your database Your entire database
Time to Setup Test 15 Minutes - 1 Hour 30 seconds
Time for results Hours, if not days Instant
Lost revenues / conversion Losing best performance
x sample size



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