Subject lines play a crucial role in the success of a brand’s mobile marketing efforts. Given the small size of mobile phone screens, brands must think not only about content, but also about character count.

L2’s Mobile report finds that shorter subject lines drive higher open rates. Titles with fewer than 10 characters saw a 23.8% open rate during the study period; in contrast, emails with 61 to 70 characters in their title garnered a 21.5% open rate.

Mobile

Encouragingly, brands seem to be paying attention: the average character length of email subject lines decreased from 43 to 38 between August 2016 and 2017. However, iPhones typically truncate subject lines at 35 characters, meaning that brands could stand to shorten them even further.

Subject line lengths vary by sector. Consumer electronics brands tend to cut them off at around 25 characters, while department stores and big box retailers — the only brands in L2’s study that recorded longer subject lines this year than last — averaged 48. This may seem like a sound strategy for brands with large inventories and multiple simultaneous sales. But despite efforts at segmentation, the vast majority of these emails go unopened.

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