My Tried-and-True Best Practices for Crafting Compelling Subject Lines
Subject lines play a crucial role in determining whether your audience will open and engage with your emails. Over the years, I have developed and refined a set of best practices for crafting compelling subject lines that grab attention, drive engagement, and convert subscribers.
In this blog post, I will share some of my key tried-and-true techniques, derived from continuous A/B testing, to help you optimize your subject lines and boost your email performance.
Without further ado, let's dive in.
Best Practices for Subject Lines
#1 Keep it Short and Punchy
Your subject lines should be concise and to the point. Aim for 48 characters or less, including spaces, to ensure your entire subject line is visible across email clients and on mobile devices, and to make it easier for readers to quickly understand the email's purpose.
If you have a long subject line, remove unnecessary words or, at least, front-load it with the key info so that your subscribers can grasp the critical part of your message immediately.
The SL in full: “Explore The World of Williams Sonoma | Thoughtfully designed and crafted with care”. I’d either move the second part to the preheader section or rewrite both the SL & PH.
Source: Williams Sonoma
#2 Drive a Sense of Newness
In general, terms that introduce a sense of newness, such as “meet”, “introducing”, “save”, “x% off”, and “limited edition” drive higher open rates because subscribers haven’t seen the email content before. To increase open rates even further, pair these compelling terms with personalized content, like the recipient's first name and order. Here's an example:
Yes, please!
Source: Doordash
Though, don’t personalize just because. Make sure it aligns with your strategy and goal so you can use personalization with maximum effectiveness.
#3 Pique Your Recipients’ Curiosity
This ties to the previous point, but emphasizes the sense of curiosity. Curiosity-inducing SLs often create a “Curiosity Gap” that can only be filled by opening and reading the email. The easiest way to generate a sense of intrigue is by posing a question in your subject line, which the email will answer. For instance:
Have you heard?
Coming Soon…
New arrivals you don’t want to miss
These are all excellent examples that encourage recipients to open your email to explore the content inside.
#4 Drive Actions and Be Direct
For campaigns that demand a specific action, such as a product launch or a sale, clear and actionable subject lines usually result in the most opens since they clarify what you want your recipients to do with your email (and that's why CTAs exist!).
By including words like "Meet" and "Save," you set expectations, and recipients are more likely to act as you intended. Here are some effective actionable and direct subject lines:
[Product Launch]
SL: Meet The Medium Everywhere Bag
PH: Sized just right for an overnight stay.
[Sale]
SL: [Name], the Outlet Sale is here!
PH: Save up to $x off your entire order only through 7/8 @ 11:59pm EDT.
[Restock]
SL: “Product Name” is back!
Of course, a direct SL can also evoke curiosity —
SL: This Just In: FREE
#5 Use Emojis Tastefully
Emoji is an excellent way to make your content more expressive and stand out in a crowded inbox. It helps improve open rates and engagement when used strategically. Before adding emojis to your subject lines, keep these in mind:
Check the render: Emojis can display differently across devices. Make sure you test and preview your email in various email clients (Gmail, Outlook, etc.), browsers, and mobile devices and desktop to ensure they display properly. With tools like Litmus, you can test and preview 100+ popular email clients in seconds.
Don’t Go Overboard: Overusing emojis not only makes your email look spammy, but could also trigger spam filters causing deliverability issues.
Love the chubby one 👀
#6 Look at the Bigger Picture
Your SL, PH, Sender Name, and even Email Address all work hand-in-hand. Think of these elements as complementary parts of your subject line working together to form an even more persuasive message.
Take this example from Misen:
Rather than just "Misen", the sender name includes "Cyber Monday" to differentiate itself from other brands, indicating that this is a sale email subscribers shouldn't overlook. So, get creative!
A/B and Multivariate Testing
Testing can reveal what resonates well with your audience.
Create multiple versions of the same email, varying only the subject line, and then send them to a group of randomly selected subscribers, large enough to get a statistically significant result. Most ESPs, like Klaviyo, offer a snapshot of test results within their campaign reports:
Klaviyo’s Test Results tab includes winning variation, win confidence, statistical significance, winning metric, and test size.
When assessing the results, make sure you look beyond open rates — click metrics and conversion metrics are also important — as a compelling (or un-compelling) SL could affect bottom-funnel metrics.
Note
With the release of iOS15, Apple Mail Privacy Protection (MPP) changed the way that ESP receives open rate data by prefetching tracking pixels, leading to inflated open rates on email campaigns.
Therefore, I recommend generating two separate reports before assessing your test result: one report that incorporates the MPP property, and another that don’t. Comparing these reports will enable you to discern the genuine impact of the subject line variants amongst your audience.
Next Steps
Start experimenting with different SLs + PHs to find out what engages your audience! Build your own guide so you can maximize email performance while improving email development efficiency!
