# 786

Embedding Images In Email

In ShortEmbedded images in email rarely render well and usually do nothing but increase file size. The article’s test results show that image embedding does not solve image blocking in a dependable way. Instead of producing a local copy of the image that every client can display, embedding turns the image into encoded text inside the message and makes the email heavier before it is even opened. In practice, that creates a larger download without…

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In Short

Embedded images in email rarely render well and usually do nothing but increase file size. The article’s test results show that image embedding does not solve image blocking in a dependable way. Instead of producing a local copy of the image that every client can display, embedding turns the image into encoded text inside the message and makes the email heavier before it is even opened. In practice, that creates a larger download without producing a reliable visual result.

With the well known growth in image blocking by email clients, some customers have been looking for alternatives to linking web based images into HTML emails.

Some years ago, image embedding used to the standard way images were included in emails. It differs from linked images in that the image itself is actually encoded, and included inside the message.

So once you have downloaded the email, you are not reliant on a web connection to view the images, because you have it all locally. It sounds perfect, except for a big increase in email size vs downloading just the HTML and then the images afterwards.

We get asked fairly often why we don’t allow image embedding to work around image blocking. Our position (‘It is not worth it for the cost in filesize) has been based on testing done some years ago, before image blocking was so common. So we though it was time to update our test results.

Testing embedded images in email

Here’s the recipe for creating HTML emails with embedded images:

  • Take one HTML page, with your text content and CSS
  • Grab an image you want to send embedded in your email
  • Use a Base64 encoder to turn your binary photo into a huge text string
  • Replace your normal image source with that string
  • Save your file and send as normal

When you have added your encoded image, you end up with an HTML document which looks something like this:

You will notice you have an enormous text file if you are encoding any kind of photograph. I took this file, and sent it out to a bunch of the major email clients, to see if they would render it.

Embedded images test results

The results were almost uniformly bad. Of all the email clients we tested, only Apple Mail showed the photo at all (and it shows linked images by default anyway).

Apple Mail Showed perfectly
Entourage 2008 Alt attribute and image outline only
Gmail Alt attribute and missing-image outline only
Windows Live Hotmail A grey block with no alt attribute
Outlook 2003 Alt attribute and missing-image outline only
Entourage 2007 Alt attribute and missing-image outline only
Thunderbird 2 Alt attribute, no missing image outline
Yahoo! Mail Alt attribute and missing-image outline (Classic & New)

So based on our results, it is clearly not worth using embedded images in your emails. All you will be doing is forcing people to download encoded images that they will not be able to view.

Instead, the best course is to follow our normal design guidelines and design your emails knowing that some people will not see your images.

That means making sure your copy stands alone, and that it is visible high enough for people to see if images are blocked. Don’t forget to link prominently to a web version too, especially if your images are particularly important.

Related Insights

Frequently asked

Why do embedded images fail when linked images are already blocked?
Embedded images change the delivery method, but they do not change how email clients handle image display. The article’s results show that many clients still refused to show the embedded photo, even though the image lived inside the message. That means embedding does not bypass the core problem of image blocking in a reliable way.
How does embedding compare with linking images in HTML email?
Linked images load from a web location after the email opens, while embedded images are encoded into the email itself. Embedded images remove the dependency on a web connection for the image file, but they increase message size and still produced poor rendering in the test results.
What is the main technical cost of embedding images?
The main cost is filesize. The article says the image becomes encoded text inside the message, which creates an enormous text file when the image is a photograph. That makes the email heavier before the recipient even opens it.
When does image embedding not apply as a useful fix?
It does not apply when the goal is to work around image blocking across major email clients. The test results showed that most clients still did not display the embedded image, so embedding does not solve the problem it is meant to solve.
What did Apple Mail do differently in the test?
Apple Mail showed the embedded photo perfectly. The article also notes that Apple Mail shows linked images by default, so its result does not prove that embedding is broadly reliable across email clients.
What did Gmail and Yahoo! Mail show for embedded images?
Gmail showed only the alt attribute and a missing-image outline. Yahoo! Mail showed the alt attribute and a missing-image outline in both Classic and New versions.
What did Outlook and Entourage show in the test?
Outlook 2003 and Entourage 2007 showed the alt attribute and a missing-image outline only. Entourage 2008 showed the alt attribute and image outline only. The shared pattern is clear: the embedded photo did not render normally.
How should email content be designed if images may be blocked?
The article says the copy must stand alone and the most important content must appear high enough in the message for readers to see it without images. That means the message should still communicate its meaning when the visual layer fails.
Why is a web version still important if images are embedded?
A web version gives recipients a place to view the full design when the email client does not render images properly. The article says to link to it prominently, especially when the images are particularly important.
Is image embedding worth testing for every email program?
The article’s answer is no for the general case. The observed result was that embedded images were not worth the cost because they forced recipients to download encoded images they often could not view.
What is the practical trade-off between local viewing and larger email size?
Embedding creates a local copy inside the email, so the image does not depend on a live web connection after download. The trade-off is that the message grows much larger, and the article’s tests show that this larger file does not buy dependable rendering.
Does embedding preserve the image better than a missing-image placeholder?
No. The article shows that many clients still replaced the image with alt text, outlines, or grey blocks. In other words, embedding did not protect the visual experience from failure; it only made the failure heavier to deliver.
What decision does the article reach on embedded images overall?
The decision is that embedded images should not be used as a workaround for blocked images in email. The article says the better course is to follow normal design guidelines and assume some recipients will not see the images.
What should be evaluated before choosing embedded images in a business email system?
The article’s test-driven logic is to evaluate rendering reliability and filesize before using the technique. A business should not assume a local image copy is an improvement unless the clients it matters to can actually display it.

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