Are AI Generated Subject Lines Effective?

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Can Using AI Generated Subject Lines Increase Lift?

Prior to the introduction of artificial intelligence (AI), creating multiple email subject lines took a lot of time and resources. But these days, AI content generation tools like ChatGBT, Jasper, Anyword, and others can create not just one or two, but many subject lines in as little as seconds. This can provide email marketers with a wide range of new creative options. But are the resulting AI generated subject lines effective?

To determine the effectiveness of subject lines – whether created by AI or a human – you have to test. Traditional A/B testing methods typically compare two or more subject lines using segments of your audience. This can be time consuming and – if one of the subject lines tested really fails – costly. We wanted to know how using AI to increase the volume of subject lines tested might impact opens and clicks.

The Analysis

We conducted an analysis to determine the lift in email response when multiple AI subject lines were tested. We took advantage of a virtual testing platform, Subject Line Pro, that is capable of delivering real results in seconds. This enabled us to analyze data from over 500 billion campaigns to discover the correlation between increases in open and clickthrough rates as the number of subject lines tested increased.

Our analysis showed that while testing 2 subject lines results in an average 3% lift in opens and little or no lift in clicks, increasing the number of subject lines tested to just 3 resulted in 21% more opens and 42% more clicks. That’s good news for marketers creating and testing subject lines the traditional way.

But what if we used AI to quickly and cost effectively generate 10 subject lines to test? We discovered that by testing 10 subject lines, opens increased by 81% and clicks jumped 242%. The click to open rate increased 128%.

Clearly the more subject lines you test, the bigger the lift in opens and clicks you can expect. Therefore, it stands to reason that using AI to create tens or even hundreds of subject lines quickly and inexpensively could be very beneficial. However, email marketers that use traditional A/B testing could run into a bottle neck that moots the advantage. That is why we recommend a virtual testing tool like Subject Line Pro.

Subject Line Pro enables you to test 10 subject lines at a time against a simulation of your own data or the platform’s database of more than half a billion subject lines spanning many key sectors. It predicts performance within 1 to 2% of actual clicks and opens in a matter of seconds.


AI subject line generators offer exciting new creative options email marketers. When combined with a virtual testing platform like Subject Line Pro, they can significantly reduce the time and expense of creating and testing subject lines, while dramatically increasing the lift in opens and clicks. 

Disclaimer: The maker of Subject Line Pro, Alchemy Worx, is a WebFactorE client.