Embedding images in email? Consider these 3 techniques


Images have proven to be one of the most compelling and information-dense media available to marketers today. A good image can communicate emotion, transmit knowledge and get that critical engagement leading to a purchase.

Every marketer needs to consider including images across their media, and email is no different. There is, however, a big caveat for images in email: They can be notoriously difficult to work with.

If not handled well, embedding images in an email can affect deliverability, engagement and sender reputation. Appearances in a recipient’s inbox also can change from email client to email client.

To get around these issues, it’s critical to understand the usable methods for embedding images in emails, as well as their benefits and drawbacks.

Senders today primarily have three different methods for embedding images at their disposal: CID tags, inline embedding and linked images. But before using these methods, email marketers should take a close look at how their active recipients behave with current emails.

The importance of analyzing recipient behavior before using images cannot be overstated. You will need to know what email clients to design images for, what size is optimal for these email clients, how these clients treat ALT text and how they both do and do not render images for recipients.

Analytics done? Great. Let’s jump into our first image-embedding option, the humble CID tag.


CID (Content-ID) has been used for quite some time to send media via email. Though dated, it’s still a viable option.

CIDs are fairly easy to understand when it comes to email: Attach the image to the email and reference it with HTML tags in the email’s template. This embeds the image when it’s opened.

While using CIDs may sound simple, the actual process can be fairly complicated, with mixed results. For example, CIDs work well with desktop email clients, but they do not play well with browser-based email.

Additionally, embedding images in this manner increases the size of your overall email, which can hinder deliverability.

Inline embedding

Compared to CID, inline embedding is a much simpler solution to embedding images. The downside? It’s not as versatile as CID, and it shares CID’s problem with increased email size.

Inline embedding requires you have a base64 string — a type of encoding scheme — of your image. But with that encoded string, you can simply embed your image into your email through a standard HTML tag and be done. No deep dives into MIME or code are required.

However, inline embedding does not play well with webmail services and is blocked completely by Microsoft Outlook. These are likely significant chunks of your email lists, which means you’ll need to plan around inline embedding’s shortcomings if you’re to deliver images successfully.

Linked images

Finally, there are linked images. Unlike the CID and inline embedding techniques, linked images are simple to implement and light on email sizes. The one complication, however, is how many recipients you’re sending an image-laden email to.

If you’re sending an embedded image to a smallish number of recipients (a few hundred, for example), then a typical cloud hosting site like Box, Google Drive or Dropbox could help deliver that image. If you’re sending an embedded image to tens of thousands of people, however, you will need to look into a Content Delivery Network, or CDN.

CDNs essentially host your images across a network of data centers. Emails designed with an image in mind will then call on the CDN-hosted image through an embedded HTML tag. That’s it.

Linked images are simple: They keep email lightweight and allow you to make adjustments to the image through simple changes to HTML tags.

However, using linked images does present a few downsides. Namely, it requires an email to download an image from external servers, which could lead to latency issues.

Additionally, it can succumb to the same blocking issues that CID and inline embedding suffer from. So, while linked images may sound good at first glance, they may not offer any tangible benefits over the other image-embedding techniques.

Regardless of what embedding technique you use, you’ll need to have a crystal-clear understanding of who is going to look at your email and where they’ll look at it. Your design team will need to prepare and design email images for mobile, desktop and web browsers for an almost endless supply of email services.

Still, the effort to stand out from the crowd and build a stronger relationship with your recipients can be worth it.

Opinions expressed in this article are those of the guest author and not necessarily Marketing Land. Staff authors are listed here.

About The Author

Scott Heimes serves as Chief Marketing Officer at SendGrid, where he is responsible for the company’s brand strategy, driving demand for its solutions and leading global marketing operations. Scott oversees corporate marketing, demand generation, corporate communications, partnerships and alliances, international expansion and SendGrid’s community development team.



Please enter your comment!
Please enter your name here