Embedding Images

Supported Image Formats

Our API supports embedding images within the body of your email using the following methods:

  1. Linked images - this is the recommended, modern method for including images in your email.

  2. Content-ID images - we have built this as a fallback for legacy applications that are unable to host images on the Internet; this could also be used for images that are dynamically generated by your application.

Note that this is distinct from attaching an image to an email, which will typically require your recipient to click on the attachment to view the full-size image. For more information on attachments, see here. In contrast, embedded images are displayed within the body of your emails.

Linked images vs Content-ID images

Advantages of linked images

  • Emails are smaller in size as the image are hosted on a server elsewhere

  • Better support by email clients

  • Doesn't count towards the limit on the number of attachments an email can have

Advantages of content-ID images

  • Images exist entirely within the email; API user do not need to host the image separately

  • Intranet recipients do not need to connect to the Internet to see the image

More Info

For more information, see the section on linked images and content-ID images respectively.

How About Base64-Encoded Images?

We do not officially support base64-encoded images for the following reasons:

  • Popular email clients like Gmail do not support base64-encoded images and your recipients will not be able to see the images.

  • Emails with base64-encoded images are significantly larger, are more likely to be clipped by email clients (for more information, see here) take longer to send, and are more likely to be marked as spam.

If your use case requires dynamically generated images and you are unable to host your own images on the Internet, we recommend that you look into Content-ID images as a replacement for base64-encoded images.

While we do not officially support base64-encoded images, we do not prevent you from sending them. If you choose to do so, please note that you have to stay within the email size limit.

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