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Using data URIs to embed images in email has continued to attract a respectable amount of interest since our original post in 2008. While the results then were disappointing, we thought we’d give them a refresh to see if it’s now a viable workaround for those who can’t stand image blocking in email clients.

First, I personally have to admit that I’ve always approached image embedding with a sour dollop of skepticism, given this technique’s track record of:

  • Sloppy support in email clients
  • Producing large email file sizes, since the image data is embedded in the HTML file as a huge text string
  • Adding attachments to the email message (when images are embedded as a data URI in MIME Multipart/Related content)
  • Being a technique used by spammers (and penalized by spam filters)

Nonetheless, its popularity has endured, generally because of the promise that embedding is a legitimate workaround to image blocking in email clients. But is this still true now?

The lowdown on inline embedding

Before we go elbows-deep into the results, it’s worth mentioning that we’re going to look at support for inline embedded images only. Unlike the aforementioned MIME Multipart/Related content method, this is something you can try at home, in your Campaign Monitor account, without having to source your own scripts or specialized tools. However, if you’re comfortable with rolling-your-own multipart messages, you’re more than welcome to share your experiences with us in the comments below.

To get testing, we base64 encoded a JPEG image, as per the recipe described here. The resulting text string looked something like this:

<img alt="Embedded Image" height="128" width="128" src="data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEASABIAAD....snip..." />

Using this hot mess, we added the image to an email and tested away. Sadly, the results across the most popular email clients were almost as choppy as before:

Email client Embedded image displays? Comments
iOS Mail Yes
Outlook 2003 Yes All images blocked by default
Outlook 2007+ No ALT text is replaced by ‘Linked image cannot be displayed’ in 2010+
All images blocked by default
Outlook.com (Hotmail) No Grey ‘blocked image’ placeholder displays, no ALT text
All images blocked by default
Apple Mail Yes
Yahoo! Mail No Placeholder and ALT text display
All images blocked by default
Gmail No Placeholder and ALT text display
All images blocked by default
Android default Yes All images blocked by default

The word is out – embedded images in email do not evade image blocking. In the case of ‘the Outlooks’1 above, not only were the images blocked, but they largely remained blocked, even when the other images in a newsletter were downloaded. The majority of email clients which reliably display embedded images (being Apple and iOS Mail) don’t block images by default, making this technique redundant.

Now, it’s over to you – have you used encoded images successfully in your campaigns? Why? Examples and lively discussion are welcomed in the comments below.

1 By the way, ‘The Outlooks’ is my future indie-band name, hands off yuppies.

This blog provides general information and discussion about email marketing and related subjects. The content provided in this blog ("Content”), should not be construed as and is not intended to constitute financial, legal or tax advice. You should seek the advice of professionals prior to acting upon any information contained in the Content. All Content is provided strictly “as is” and we make no warranty or representation of any kind regarding the Content.
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