There’s no shortage of advice (not all of it consistent) about how to write an effective email subject line.

In general, though, shorter subject lines do better.

This blog post of 164 best email subject lines to boost your email open rates (note: it actually lists only 100) offers no advice at all about how long your subject line should be, but we noticed that its examples average only 34 characters.  (We counted. One example, “Hey”, uses just 3.)

And according to data from Marketo, 41 characters (or roughly 7 words) appears to be ideal for maximizing your click-to-open rate.

 

What our data tell us

When you use our Advanced Search options you’ll find it’s easy to identify emails with Tiny, Optimal and Too-long subject lines.

In fact, after conducting advanced searches on recent trends in subject line length, we found that our data tell us:

  • Tiny subject lines (0-25 characters) range from 14% to 16% of all emails
  • Too-long subject lines (over 55 characters) hover between 23% and 24%
  • Optimal subject lines (0-55 characters) make up the “just right” majority—nearly 78%

Indeed, if we examine the millions of emails we’ve received since we began collecting and indexing them, we find that Optimal subject lines make up fully 75% of the total.

 

Why shorter subject lines might do better

There are two popular theories to explain why shorter subject lines might outperform longer ones.

First, their brevity typically piques recipients’ curiosity—prompting them to open your email to find out what it’s about. Second, many email clients—especially those on mobile phones—display fewer than 50 characters in the subject line and truncate those that run longer.

Below you’ll find a breakdown of the number of characters displayed on a client-by-client basis:

The Orchard Email Client Chracter Length screencap

What’s the ideal subject line length for you and your subscribers? There’s only one way to find out: Test.

 

Testing issues to keep in mind

When preparing a test, be aware that it’s all too easy to resort to subject lines that are gimmicky or sound spammy. Your challenge as a marketer is to write a lean subject line that intrigues your subscribers without deceiving or misleading them. It’s the same concept as writing quality content for top email marketing blogs.

And don’t forget that your preheader text acts as your invaluable second subject line. Make sure your subject line and preheader text work in sync to complement each other.

Of course, you can also test to see exactly how your email will show on mobile devices.

 

Short subject lines from long-established brands

When we first published this blog post several years back, we featured email subject lines from the following 4 brands. As we were updating our examples, we noticed these businesses are still keeping it short and sweet.

Daily Overview

Every day, Daily Overview sends one beautiful image taken from a satellite. As a subscriber, you immediately know what their email is about because the subject line tells you:

The Reformation

This fashion brand’s emails are known to rely on gorgeous images and minimal text. In fact, Reformation’s views on minimal text within the email extend to its views on minimal text in subject lines:

Etsy

The Etsy team does a delightful job of keeping it short and sweet. Their subject lines jive well with the content of each email:

BuzzFeed

Known for its humor and viral content, BuzzFeed uses short subject lines to prompt curiosity and drive opens:

 

Not everyone thinks shorter is better

Our data show that optimal subject lines (those with no more than 55 characters) do represent the vast majority of marketing emails—and have done so for years. But is there evidence that subject lines we consider too long may actually work better than shorter ones?

Reviewing a study of 1 million email subject lines, a prominent marketing expert notes that “over 60 characters generated higher open rates than those between 21 to 60 characters even though the end might have been cut off when viewed on a smart phone.” His study suggests that the key to a successful long subject line is to make sure it contains “multiple propositions”—for instance, by promoting an explicit time-limited discount on specific name brands.

Still, this expert concludes with the same common-sense advice we’ve already given you. “Whichever way you look at it”, he says, “one thing is certain: you HAVE to TEST. Decision making without testing is just guesswork.”

Editorial Image by Gerd Altmann from Pixabay