The ultimate guide to compelling email subject lines: data-driven best practices + 21 examples
It’s no secret—email is one of the most powerful marketing tools.
The ability to reach your audience directly without social algorithms and higher conversion rates compared to PPC ads make email a go-to channel for every marketer. But as a result of this fact becoming well-known, it’s now harder for businesses to stand out in a crowded inbox.
The first step to getting readers’ attention is creating a compelling email subject line. Here’s when things get tricky.
The harsh reality: there’s no secret formula for crafting effective subject lines.
The good news: based on data, best practices, and tests, you can learn what works best for your target audience.
Maybe you’re wondering:
- What are the top-performing email subject lines?
- What are the best practices to boost open rates?
- How are other businesses nailing the email marketing game with catchy subject lines?
- What do other email marketing experts do (and what advice would they give)?
We’re going to answer all of those questions and more.
First things first: Before we dive deeper into the email subject line best practices, let’s cover the basics and address the most frequently asked questions around email subject lines.
Long vs. short subject lines: which one is better?
Subject lines should be a teaser that encourages customers to open your email.
Klayvio’s data shows that subject line length and open rates are inversely proportional—the longer the subject line, the lower the open rate.
Research also shows 63% of emails are now opened on a mobile device. With so many people reading emails on their mobile devices, brevity is especially important (as most screens only display 30-40 characters in a subject line.)
The bottom line: Shorter subject lines often perform better, but you’ll need to A/B test to see if that rings true for your unique audience.
ALL CAPS in the email subject line—yes or no?
Shouting might get peoples’ attention in person, but using all caps in your email subject lines (which feels like shouting) does the opposite.
Our research shows that email marketing campaigns without fully capitalized subject lines performed about 12% better than campaigns with subject lines in all caps with a roughly 2% higher absolute median open rate.
Another detail to consider is the difference in the performance of emails between companies that often use caps in their subject lines versus companies that don’t. Our research indicates only 2.5% of companies write all or most of their emails with subject lines in all capital letters.
For these companies, this stylistic choice is part of their branding, and they find that it works well for their audience when used consistently. Clothing brand is one brand that leans into the all caps subject line approach:
The bottom line: In general, it’s smart to lean away from all caps, but remember—it depends. Experiment and see what works for you.
What about punctuation marks in the subject line?
There’s nothing wrong with using punctuation marks in subject lines—until you overdo it.
Our data shows campaigns that use a series of consecutive exclamation points or question marks performed about 19% worse than campaigns that did not.
The bottom line: Don’t be spammy. Avoid using all caps, too many punctuation marks and symbols, and SPAM-triggering phrases like “JUST THIS ONCE FOR A LIMITED TIME ONLY,” “100% FREE!,” and/or “ACT NOW!”
The best way to come up with ideas for email subject lines with high click-through rates is to check out some top examples and analyze the patterns that emerge there.
Here are 11 best practices for email subject lines we’ve found that will help your emails get opened (and read!) more often.
Use personalization for your emails
People crave personalized experiences and dedicated attention. Something as simple as using the reader’s first name in an email can help you boost open rates.
According to Invesp, open rates with the recipient’s name in the email subject line have an 18.30% open rate, compared to a 15.70% open rate for subject lines without a name.
But personalization doesn’t stop there.
Collecting data with the knowledge, permission, and explicit consent of your prospects and customers will put you ahead of the competition by opening endless personalization opportunities. This is why it’s increasingly important to collect Customer-First Data™ and create a personalized shopping experience.
Clothing brand Jenni Kayne, for example, uses a subject line that references a shopper’s favorite items, which taps into customer data around individuals’ product preferences.
Evoke a sense of curiosity in your headlines
Humans have a natural impulse to investigate, observe, and gather information. Teaser-style subject lines can leverage that natural curiosity and encourage customers to open your email just to find out what’s inside.
“Use curiosity as much as possible; it’s one of the greatest emotional drivers humans have. Do your best to create as much of it as you can in your subject lines. Instead of a subject line like: ‘One doctor’s tip for better health,’ use something like: ‘Why America’s #1 doctor says do NOT eat broccoli,’” says Chase Dimond, an email marketer, on Twitter.
The Sill is a popular online houseplant retailer selling a wide variety of indoor houseplants. They do a great job crafting email subject lines that spark curiosity via information gaps:
Ask questions in the subject to urge readers to click
Asking questions urges readers to open the email and find out the answer. It’s another form of curiosity and tapping into our information-seeking brains.
If you use this tactic, make sure to ask interesting questions to pique the recipient’s interest.
Just remember: By including a question in the subject line, you’re setting an expectation. Be sure to provide the answers the reader is looking for in the body of your email.
Make your subject lines conversational
A conversational and friendly tone of voice is far better than a robotic statement in the context of email subject lines. People tend to pay more attention when you talk directly to them.
A good rule of thumb when writing an email subject line is to imagine you’re writing to a close friend. If you wouldn’t write something to your friend, it’s probably better to avoid it altogether.
“My only advice for email subject lines is to think of them as starting a conversation rather than making an announcement. Focus on your customers rather than your brand. Ask yourself: Why should they care?” says Samar Owais, a SaaS & ecommerce email strategist and copywriter, on Twitter.
Consider context for every email subject line
Imagine if customers had a dedicated inbox just for your emails. Sounds great, right?
Unfortunately, this is far from reality, which is why you should consider every other aspect that might affect the performance of your emails.
“Consider the context. By context, I mean the inbox. What kinds of emails does your subscriber usually receive? Will emojis/questions/whatever style subject lines you’re writing stand out or blend in?” says Nikki Elbaz, an email copywriter, on Twitter
For example: What day are you sending the email, and at what time? Study your email sends and open rates over time to see when they are highest.
Klaviyo’s Smart Send Times makes figuring this out super simple.
Include the offer in the subject line heading
When you have a specific offer for your customers, including it in the subject line is a smart way to bring a higher conversion rate.
Being straightforward and telling customers what they can expect inside the email can help you reach a high-intent audience.
“Include the offer in the subject if it’s a sales-based email or product launch. The open tends to be lower, but the intent is much higher,” says Jacob Sappington, a partner at Homestead, on Twitter.
The women’s clothing label, Good American, sent an email with the subject line: “The Denim You Need, Only $99.” Although customers who aren’t in the market for denim at the moment likely won’t open the email, those who are will have a much higher likelihood of making a purchase knowing there’s a deal going on.
Create a sense of urgency as a hook in the subject line of the email
The fear of missing out is one phenomenon that can drive customers to act quickly. It’s also a great hook for an email subject line.
If you’re looking for a way to get people to act, create a sense of urgency. A great example is promoting a sale and reminding customers of a discount that’s about to end. Creating a limited-time offer (like for a specific event or holiday) can help you boost email open rates.
Floyd is a direct-to-consumer furniture brand that created a sense of urgency with a series of emails promoting the President’s Day sale.
Playing with different subject lines, Floyd reminded subscribers to use the offer and save on their next purchase before the discount went away.
Use a specific subject line for your email
Specific email subject lines let the reader know exactly what to expect when they open your email. How long will it take for customers to see the first effects? Or how much weight can they lose? How long does your earbuds’ battery last?
Being specific gives readers a strong reason to open your email as it eliminates uncertainty.
“Whenever possible, be specific – specificity almost always wins. Instead of ‘How I lost weight by eating Cheetos,’ write something like: ‘How I lost 13 lbs. in 3 days eating Cheetos,’” says Dimond.
Use numbers to drive curiosity right at the beginning
Using numbers in your email subject lines can dramatically increase your open rates. A study from Yesware found that subject lines that include numbers get a 45% higher open rate than the average.
The sparkling water brand Aura Bora uses numbers (in the form of a percentage off discount) in their email subject lines to grab readers’ attention and to encourage them to open the email.
Test emojis, but don’t overdo it
If you want to stand out in a crowded inbox, using emojis might be an effective way to get noticed. While emojis are widely adopted in online communications, you should consider some basic rules to avoid misinterpretation.
Use emojis to amplify the message rather than to replace words. Your main goal is to deliver a clear message to your subscribers.
Drunk Elephant, a popular brand among skincare enthusiasts, often uses emojis in its email subject lines to stand out in the inbox with a pop of color and to bring in a fun tone that aligns with their brand voice.
Also, don’t forget that emojis are shown differently depending on the operating system your subscriber is using, so make sure to A/B test across channels and devices.
BONUS: Preview text is important real estate—use it
We can’t talk about subject lines without mentioning the importance of preview text.
You can use the preview text section to give readers a sneak peek into your email. If you don’t set the preview text, the email client will automatically use the first sentence of your email copy, wasting an opportunity to drive opens.
Instead of leaving preview text empty or repeating the subject line, add another sentence to pique the reader’s interest.
The amount of text shown depends on the email client and the device the customer uses to check the email, so be sure to always test email subject lines before sending.
To help you create effective email subject lines, we’ve dissected hundreds of emails from some of the leading DTC and retail businesses. Note that what is the best email subject line for one brand will be different for another. This depends on your brand, your email list, and more.
Here are 10 great email subject lines and why they work.
Atoms creates an emotional response in its emails
Subject line: Your Dad is the Greatest
Why it works: Evokes emotions and creates an emotional response
The direct-to-consumer footwear brand Atoms sent an email for Father’s Day with a short and effective subject line, “Your Dad is the Greatest.” The strong personal appeal is designed to create an emotional response, and it’s often used as a marketing tactic to drive results.
Caraway triggers a users curiosity through its marketing
Subject line: Are You Cooking With Toxins?
Why it works: Asks questions and triggers curiosity
The Instagram-famous cookware brand Caraway uses questions to trigger readers to open their email newsletters. As more people focus on taking care of their health than ever before, creating curiosity by discussing important topics such as possible threats by cooking with toxic cookware can boost open rates and bring more sales.
Fenty Beauty offers a sense of urgency and a discount
Subject line: LAST CHANCE! Enjoy 25% OFF
Why it works: Creates urgency and offers discount
Fenty Beauty is a great example of how to use all caps and punctuation marks without overdoing it. The cosmetics brand uses a combination of capital letters and sentence case formatting to highlight the urgency of the time-limited sale while also showing the offer in the subject line, so customers can know what to expect.
Chubbies targets its athletic audience in the email
Subject line: Your new gym outfit
Why it works: Targets a specific audience and sparks curiosity
If you’re a gym fanatic or you’ve been thinking of going to the gym, you couldn’t resist a subject line that says “Your new gym outfit.” Premium apparel brand Chubbies targets a specific high-intent audience and makes it irresistible not to check what your next gym outfit might look like.
House Of Harlow 1960 creates a FOMO in the email
Subject line: Our most popular necklace is back in stock!
Why it works: Triggers curiosity and creates a fear of missing out (FOMO)
If something gets out of stock quickly, it must be good, right? A subject line that says, “Our most popular necklace is back in stock!” makes customers want to check it out immediately. House Of Harlow 1960 is a well-known jewelry brand that uses this tactic to inform customers when a bestseller is available again.
Natori gives customers a special offer in their marketing
Subject line: Express Delivery For V-Day
Why it works: Creates urgency and gives customers a special offer
Finding the right gift is always a challenge and getting it on time during peak season becomes even more daunting. The luxury clothing and lingerie brand Natori created a special offer with express delivery for Valentine’s day for limited-time orders, urging customers to react quickly.
Kylie Cosmetics gives a free gift offer
Subject line: Buy a Lip Kit, get a FREE gift!
Why it works: Offers an incentive
Offering a free gift with purchase is one of the oldest marketing tactics—and it still works! If you can incentivize customers with a gift, use that trigger in the email subject line to boost open rates and ultimately increase sales. One of the most popular brands, Kylie Cosmetics, uses this tactic to sell more lip kits.
Lively chooses to use UGC in the subject
Subject line: “I just did a yoga workout; the ladies stayed in their seats the entire time…”
Why it works: Uses customer review in the subject line
Using customer reviews as an email subject line is a powerful storytelling mechanism that urges readers to discover the whole story. Lingerie brand LIVELY experiments with different types of subject lines, using the power of customer reviews to spice up their subject lines with storytelling, credibility, and social proof.
Puma gives a discount code in their email marketing
Subject line: To one year. Take $25 off to celebrate.
Follow-up subject line: Don’t forget! Your $25 code expires soon.
Why it works: Creates a personalized shopping experience
Celebrating mini-anniversaries with special offers can help you create a personalized shopping experience and build a strong customer relationship. Puma uses this tactic to encourage customers to make a purchase using a discount code. The footwear brand also uses a follow-up email to remind customers of an expiring time-limited offer.
Tatcha promises customers results with its product
Subject line: See instant results with The Rice Wash
Why it works: Gives customers a promise
Customers looking to solve a problem expect a brand’s reassurance of wanted results. However, if you decide to make a promise, make sure to stick to it. The luxury beauty brand Tatcha uses the power of a promise to encourage customers to try the product.
Christopher Maroney-Petitt, Owner, Ecom Growers
Design email subject lines for increasing your open rate. Lead with intrigue or direct offers. The goal is to stand out among the sea of emails in a person’s inbox and don’t assume they are reading. Assume they are skimming!
Keep your subject lines to the point and don’t over complicate what you are communicating to them. Less is more and fewer words typically works better. Think about what would get you to open an email, and then do that.
Toccara Karizma, CEO, Karizma Marketing
Studies show that headlines with numbers in them can help increase your email open rates. Headlines that use the recipient’s first name also can increase open rates due to their level of personalization.
Keeping headlines short can also be helpful, as can be using preview text to hint at what is contained in the email.
Solving a pain point with a headline can also work well to encourage email opens. For example an email headline like “How to Pose in a Bikini Like a Model” to promote a swimwear brand’s blog and products can work really well with their subscriber base and offer value at the same time.
Finally adding mystery, curiosity, humor, or a question to your headline can also encourage someone to open your email.
Ashley Ismailovski, CRO Operations Manager, SmartSites
Keep your subject lines short! I know you just created the most amazing email and you can’t wait to share it with your subscribers, but if the subject line isn’t compelling, they just won’t open the message. The fact of the matter is that most emails are read on phones nowadays. This means that length subject lines could get cut off before you get to any of the good stuff!
Tennessee Allgood, Lifecycle Marketing Senior Manager, Stak Agency
Get right to the point. Sometimes indirect or vague subject lines can work in your favor, but its best to keep subject lines clear and concise. Five to 7 words seems to be the sweet spot for my clients!
Nichelle Hubley, Founder, CEO, &BAM
Different segments respond to different kinds of subject lines. Run some tests to see what segments respond best to FOMO, curiosity, self-interest, etc. Your customers and pre-customers will open based on where they are in their buyer’s journey so think “who” not “what.”
Cassie Benjamin, Email and SMS Channel Manager, Tadpull
Oftentimes a subject line that reads well on desktop may get cut off in mobile inboxes so it’s always a good idea to view your subject lines on both desktop and mobile during your testing process. Use shorter copy to ensure your enticing subject line doesn’t lose its effect on mobile.
Adam Kitchen, CEO, Magnet Monster
Be different with your email subject lines! Everybody is doing the same thing with fake scarcity. Inject a dash of humor, instead. Throw your customers a curveball and use curiosity as the reason to open instead of scarcity.
Morgan Mulloy, Assoc. Director of Retention Marketing, Avex Designs
Make sure your email subject line is relevant to your target market. The terminology used should appeal to that specific audience.
Abby Siciliano, Email Expert & Director Business Development, Tinuiti
Leverage the pre-header text area to elaborate on the story you’re telling.
Ben Zettler, Digital Marketing & Ecommerce Consultant, Ben Zettler Digital
Keep email subject lines concise. Ask questions. Be conversational and relatable.
Brandon Matis, Owner, Luxor Marketing
Keep your subject lines short. Four to six words is perfect.
Ready to stand out with email subject lines that get clicked?
Writing effective email subject lines is half-science, half-art. The only way to improve is to test, optimize, and repeat.
The good news is that following successful templates, and best practices from other brands can help you craft compelling and click-worthy email subject lines.
Better yet: Klaviyo customers get access to Klaviyo’s subject line assistant, so you can quickly populate subject line variations and A/B test your way to higher opens and click-throughs.