What makes a subject line “short”? Is it 25 characters, 50 characters, 75 characters? It’s assumed that there is a defined number that makes a subject line long or short. In general, people believe that less than 25 characters is short and more than 75 characters is long. So, does length matter? The answer is yes, but it depends on what’s in the subject line.
Types of subject lines:
Ambiguous - the only way to find out what’s behind an ambiguous subject line is by clicking it. These subject lines tend to generate higher opens, but fewer clicks. Since there’s no filter, people are opening it whether they’re interested in the product or not. Some ambiguous subject lines you might see:
Specific - this type of subject line tells you exactly what’s in the email. These generate fewer opens, but higher qualified clicks. For instance, see the examples below. If the subscriber doesn’t want to buy the jeans, they won’t open the email.
Single Proposition - this is what we call a subject line with only one offer or CTA. These tend to be shorter and difficult to make long because there isn’t as much information.
Multiple Proposition - These subject lines are specific and targeted to subscribers who are going to open, click, and buy. Unlike single propositions, multiple propositions can be difficult to shorten because there is a lot of information.
Let’s put some data to the question, do shorter subject lines have higher open rates?
We tested every subject line within the Subject Line Pro database. According to the data, 63% of subject lines fall between 20 and 65 characters, and these emails have the lowest open rates. The reason this length is so common is that everyone is trying to make sure their subject lines are not "too" long. Subscribers become blind to what they see all the time, but change is something that makes a difference. Subject lines don’t tend to stand out unless they’re outside of this range.
When you’re testing your subject lines, keep things fresh. According to our research, unique open rates increase if you use “fresh words” or emojis. Fresh words are defined as words that haven’t been used in a subject line for the past 6 months. Recently used words, or words that have been used more than once in the last 6 months, have lower open rates on average. This proves a previous point, if you do something often, it stops working overtime.