Subject Line Research: Response Goes Down As the Characters Go Up

Posted by Ed Taussig on

The issue of subject line length is something that gets debated endlessly around the marketing water cooler. Most people know that anything longer than 55 characters (and, just a reminder, the spaces do count!) will get cut off. And many have heard the maxim that 35 is really a better number to aim for. But, does anyone know how the length of the subject line actually affects response?

Well, yes, in fact. We did an analysis on all acquisition campaigns sent through our Postmaster Direct Network over the last two years. We found that response rate (as measured by clicks) goes down dramatically when the subject line is longer than 50 characters. How dramatic is this difference? Click-through rates for subject lines with 49 or fewer characters were 75 percent higher than for those with 50 or more.

Yowza. That’s real money that marketers are leaving on the table when they get too verbose.

What about open rates? While the difference wasn’t as dramatic, we found that subject lines with 49 or fewer characters had open rates 12.5 percent higher than for those with 50 or more. Would you be pleased if your next campaign improved its open rate by 12.5%? Yeah, we thought so.

Of course, it’s important to remember that there is more to the subject line than character count. There are plenty of 30-character subject lines that bomb. And, admittedly, some longer subject lines that perform above expectations. Testing your subject lines on your list is the only way to know what will work and what won’t. But, this research clearly shows that, in fact, brevity is the better part of valor.


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