Q: Can your resort’s email subject lines be too long or too short?

It’s a simple thing, but one that is directly applicable to every email campaign you’ll ever create: do recipients prefer a long, medium, or short subject line? Does the number of characters influence the likelihood someone will open your email? Does it make no difference at all? That’s the question we wanted to answer. So we did.

The Goods
Some of us didn’t expect to see much effect on open rates while others expected that the longest (that got cut off by the email program and browser width) and shortest (that didn’t use enough characters to provide a compelling reason to open) would do the worst.

To prove or disprove our theories, we analyzed over 250 million emails as part of this analysis and grouped each by the character length of their subject lines. We smoothed the curve by taking a running average and found something that none of us expected: the shortest and longest subject lines tended to have the highest open rates.

Why would subject lines with just 25 characters or less be compelling enough to open? And likewise, why was the lowest point at 55 characters which seems to be a great length for getting your point across?

The *New* Theories
With the data in front of us, our revised theory is as follows. First, the shortest get the clicks simply because they don’t tell too much. Like a teaser, they give you a hint, but only get you curious about what else there is to know, increasing the need/desire to open.

Medium-length subjects do provide basic details, thus removing the intrigue factor, but may not take enough space to give a compelling reason, or a variety of reasons, to open.

The longest have the space to make a compelling case (or two) to open and likely do. This is something worth testing. The next time you send an email, do a split test and try a short version as a teaser. The next time, test a longer, more descriptive version against your original or even trying providing a secondary reason to open. A difference between 14.5% and 17% is significant in terms of opens and more than worth a shot.

Don’t Miss a Beat
A new “Stash” analysis comes out every Tuesday. If you don’t want to miss a beat, follow @RyanSolutions on Twitter or use the form below to subscribe via email.