As marketers, we tend to toss images into emails without a second thought. They're like the glitter of the email marketing world — jazzing up our products, making our CTAs shine, and helping readers grasp the most important parts of our messaging.
Cool, right? Until a key metric tanks.
Then you start wondering why deliverability is decreasing, and more emails are getting marked as spam. While images can do a lot of heavy lifting, they can also do a number on load times, deliverability rates, and even campaign performance. The alternative — not including images — isn't a great option, either. Text-only emails often don't perform as well. (Plus, they aren't as nice to look at!)
Instead of scrubbing images from your emails entirely, it's time to learn how to leverage images in emails the right way—by formatting them correctly and testing to ensure they display correctly. Sound complicated? Don't worry; we'll walk you through how to ensure images look great and boost email campaign performance—instead of holding them back.
What to consider when adding images to emails
Marketers are often given a long creative leash in marketing campaigns. Flexing our creative wings is one of the best parts of the job—but you also need to make sure that cheeky image or fun infographic doesn't impact other parts of your campaign.
When including images in emails, here are four factors to keep in mind:
- Accessibility
Image-only emails might look lovely, but they frustrate subscribers who use screen readers that can't accurately describe large or complex images. Images lacking alternative text (alt text) entirely or with misleading alt text can be confusing and difficult for these populations to understand. - Deliverability/Spam
Using the wrong size or embed method can lead to rendering issues or land your message in the spam box. Emails that take too long to load might be missed by readers and result in complaints, confusion, or fewer conversions. - Brand impression
Images that don't match your branding can look like spam or reduce trust. Consistent branding isn't just for websites — it also spills over into email images. - Conversion rates
Images can significantly impact the overall performance of your email campaigns. Engaging and relevant images can capture the recipient's attention, while poorly formatted or grainy images can harm key metrics.
The right images can be a powerful driver of engagement and conversions, while the wrong ones can hinder your campaign's success and frustrate readers. We'll get into best practices a little later, but first, let's talk about how to add images to emails. As it turns out, there are several options.
Not in the mood to nerd-out with us? Skip ahead to best practices for images in email.
How can images be sent via email?
Knowing how to embed images in your email campaigns isn't just about making your emails look pretty. Understanding the different methods (and when to use them!) helps improve campaign performance, strengthens branding, and ensures campaigns resonate with a wider audience.
You have two main options when sending images: attach them as a separate file or embed them within the email content, using one of these three methods:
- CID (Content-ID) image embedding involves attaching images directly to the email and referencing them within the email's HTML using unique content IDs. This ensures the images display when the email is opened, even if the recipient is offline.
- Inline embedding refers to placing images directly within the body of the email using HTML tags. The images are part of the email's content and are loaded when the email is opened. This method is commonly used for smaller images or decorative elements, like logos.
- Linked image embedding involves hosting the images externally on a web server or content delivery network (CDN) and referencing them in the email using URLs. When recipients open the email, their email client fetches the images and displays them within the email. This reduces file size, but requires an internet connection.
Each method has pros and cons — although embedding images is generally the best path for most email marketers. Attaching images requires readers to download attachments, which can be a security risk and is sometimes blocked outright by IT departments.
This chart explores the differences and how they can impact deliverability:
Image handling by email clients
| Client | Market Share | Images blocked by default | Renders ALT text | Renders styled alt text | Additional considerations |
| Apple Mail | 57% | No | Yes | Yes | |
| Gmail | 30% | No | Yes | Yes | Gmail clips messages with a size larger than 102 kb and hides the content behind a “View entire message” link |
| Background images not supported for non-Gmail IDs | |||||
| Outlook Webmail | 4% | No | Yes, but only one line | Yes | Outlook renders just the first frame of GIF in emails |
| Outlook for Mac and 2017-2019 Desktop block images by default. | |||||
| Yahoo! Mail | 3% | No | No | No | Mobile Yahoo! does render alt text and stylized alt text. |
Source: Litmus September 2023 Email Client Market Share Report
Best practices when using images in email
When used well, images can take your email marketing campaign to the next level by highlighting product features, making CTAs stand out, and engaging your readers. Get it wrong, however, and you're likely to see your engagement and click rates plummet. These best practices will help you leverage the awesome benefits of images, while limiting the downsides.
Choose an image size and embed method that works for your audience
There's no one "perfect" image size or embed method that displays well on all email platforms and all devices. (It would be a lot easier if there were!) When possible, choose the best format for your audience. When in doubt, use file sizes and embed methods that work well for mobile devices, as 85% of US workers check email on their phones. However, the type of image matters, too. For a large infographic or a detailed product image, you may want to attach the image so users can still view the email quickly.
Stick to the right image sizes
Think of it like Goldilocks — not too big, not too small, your images need to be just right. Images that are too wide or too small can be distorted when displayed on certain devices. Aim to keep image width below 600 pixels wide and around 500 to 600 pixels tall. Also, consider the size of email overall — Gmail clips if your email message is 102 kB or larger.
Avoid image-only emails
Image-only emails look pretty — when they work. However, they also load slowly and can cause accessibility issues for users who use screen readers. Instead of seeing your lovely image, some users might just see a broken image or (if they use a screen reader) only hear your alt text. Instead, strike a balance by including a mix of well-structured text and images, ensuring your message is accessible to all.
Include alt text
Ensuring every recipient can fully engage with your content regardless of their abilities is not just a good marketing practice — it's the right thing to do. Adding alt text that clearly describes each image helps those who use screen readers. Don't use this space to stuff in keywords; rather, clearly describe the image.
Test responsiveness across viewports and email clients
To maximize the impact of your email campaigns, ensure your emails adapt to mobile devices and perform consistently across popular email clients. Test on different platforms using preview and testing tools, and pay attention to interactive elements. Do they appear correctly on iPhones, Androids, PCs, and Macs? If not, you could alienate a large portion of your email list.
Final thoughts on adding images in emails
As always—benchmarks and best practices are great, but your audience is unique and the best way to learn what works best fo them is to split test. So if you're curious to know whether a design-rich or plain-text email is more compelling for your subscribers, create a testing plan to see how your audience responds to different formats.
Some ideas:
- Send your newsletter an A/B split test and measure click-through rate
- Split your onboarding automation into two paths (one with graphics and one without) and see how it impacts engagement
The art of using images in emails is not just about the artistic side; it's about strategy, accessibility, and delivering the best experience to your subscribers. So, the next time you craft an email campaign, ensure your images display beautifully and look great across all devices. Use the best practices above, and you'll be on your way to creating emails that look great — and actually convert.
