What’s the ideal email subject line length in 2025?

What’s the ideal email subject line length in 2025?

Email subject lines are the storefront of your email campaign. If enticing enough, someone will open the email, and read the material, just like seeing an interesting window display and walking inside a store. 

However, email subject lines walk a fine line. You want to provide enough information that you can persuade the reader to open the email, but you don’t want the subject line to be so long that you lose the user’s attention or your subject line is cut off by the device’s display screen. 

In this article, we’ll walk through data and best practices to provide guidance on the best email subject line length. 

Best subject line lengths according to data

According to Twilio SendGrid’s data from Cyber Week emails, the average email subject line length is 6 words. Here are a few 6-word subject line examples so you can better picture the length.

• Black Friday Sale just got better

• Thankful for you, thankful to give

• We found something you might like

While 6 words may have been the most popular, the subject lines that performed the best were even shorter with only 2 to 4 words. These short, quippy subject lines grabbed users' attention during the busy holiday season. 

• Just dropped: winning sets

• Treat yourself to travel

• Ready, set, shop!

• Want 40% off?

When in doubt, try to keep your subject line as short as possible–the short line is typically better at grabbing users’ attention and standing out in a cluttered inbox. 

Subject line length according to your business’ data

While it’s helpful to see in general what subject line length leads to the highest open rates, the best subject line length for your business should rely on your email program’s data. Here are a few ways to hone in on subject line length. 

Determine where your emails are being opened

Review your device data. Are most of your emails opened via mobile or desktop? Mobile inboxes only display the first 33 to 50 characters of a subject line while desktop inboxes display up to 70 characters in length. By understanding where your users are opening your emails, you can better cater your subject lines to the device type. 

Also, review your most popular inboxes. Does Outlook, Gmail, or Yahoo Mail stand out among the different email service providers? Each provider has its own recommended subject line lengths.

Desktop:

• Gmail: Approximately 70 characters

• Outlook: Between 50-70 characters

• Yahoo Mail: Approximately 46 characters

Mobile:

• iPhone: 33-41 characters (depending on screen size and orientation)

• Android: 35-50 characters (varies by device and email app)

Analyze past email subject lines

Take a look at your email programs from the last year and review the emails with the highest open rate. What are the subject line lengths of those emails? Is there a pattern where super short email subject lines perform well or vice versa? Use this data to inform your subject line strategy.

A/B test your subject line length

If you don’t have enough data for conclusive results, then use your next few email sends to test subject line length. A/B testing allows you to send two versions of the same email to segments of your audience to see which version performs better. Start with a very short subject line vs. a very long one, and narrow the gap with each test to find the perfect length for your audience. 

3 email subject line best practices

We’ve written whole guides on email subject line best practices, but here are a few key takeaways to keep in mind. 

1. Avoid spammy-sounding content

You may not intend for it to be flagged as spam, but certain words often trigger spam filters or make users more likely to mark an email as spam. For an email to be opened, it needs to first be delivered to the inbox. Avoid the following words and styles to give your email the best chance of being delivered. 

• A lot of exclamation points (nothing looks spammier than a subject line that says “FREE!!!!!!”)

• Tons of emojis (one or two is okay, but keep your emoji use to a minimum)

  • Fun fact: The most popular emoji in 2023 Black Friday emails was 🔥

• Avoid dollar signs $$$ and other symbols (*&#@)

• Phrases like: cash bonus, 100% free, or double your income

There are a lot of factors that affect your delivery rate, so if you’re noticing a lower-than-average delivery rate, it may be due to other issues, such as spam traps, blocklists, and your overall sender reputation. Explore our 2024 Email Deliverability Guide for more details. 

2. Include key content at the front of your subject line

If you’re testing out longer email subject lines, keep the most important information at the front of the subject line to hook the reader. Plus, it’s likely that at least some portion of your audience reads their emails on mobile. To make sure they don’t miss the key points, you’ll want to include the high-priority information earlier in the subject line.

3. Repurpose email content

Let’s say your email is a huge flop with a very low open rate–don’t fret yet! Instead of starting from scratch, review the email subject line. What is it about the subject line that did not interest your audience? Was it unclear? Too long? Too vague?

Take the contact list and exclude those who opened the original email, then resend the email with the same content but a different subject line. This test should give you some interesting insights about what subject lines your audience is interested in.

The verdict on email subject line length

If you’re just starting your email program and you don’t have your own data to help guide you, then keep your email subject line to two to four words if possible. This short subject line approach may not be the best fit for all businesses, so monitor your email subject line and open rates to understand what your audience engages with the most.

For more information on email subject line best practices, dos, and don’ts, check out these email subject line examples.