What is alt text in emails?
Alt text (alternative text) is a short, descriptive line of text embedded in HTML to describe the content and function of an image. In email, it's used when an image fails to load, the recipient uses a screen reader or when an email client (e.g. Outlook, Gmail) blocks external content by default (leaving a blank space in its place).
Why does alt text matter in email testing?
In today’s workflows, where emails are key parts of everything from marketing campaigns to transactional alerts, images are a core part of message delivery.
Alt text ensures that your message always lands, because it means that your recipient will still understand the full flow of your email, even when viewing the images isn’t possible. In fact, writing and testing alt text is now a critical step in delivering accessible, compliant, and high-performing emails.
That’s why whether you're running email rendering tests, validating accessibility standards, or running automated checks across clients, alt text should be part of your email QA process.
Why do I have to include alt text in my emails?
1. Accessibility Globally, at least 2.2 billion people have a near or distance vision impairment, representing a significant portion of the global population. This means that there’s a good chance that a percentage of the recipients of your emails could use screen readers, and you want to give them the same access to information to the context and meaning of your images as everyone else.
2. SEO & email client comprehension Alt text also boosts SEO, because it improves image searchability (making your emails more easily discoverable in inbox searches) and this means users are more likely to be able to refer back to information within, lowering your surplus support queries.
3. Rendering fallback If your images don’t load for your users, which is common be due to network issues or client restrictions, alt text can help keep them engaged because it tells them what they should be seeing.
How do I add alternate text for images to emails?
While it depends a little on the email client you’re using, the general process is fairly standard.
When you’re working on an email template and add an image, there should be a field where you can add alt text specific to that image. There should be an alt text field for each image you add, even if it’s a background image. You might have to poke around in the email template to find it, or check the documentation for your chosen email client.
Tips for writing good alternate image text for emails
Convey the reason the image is included
It’s not enough to state what’s in the image if it’s not clear why the image was included. Think about the purpose of including the image in your email, and make sure this is incorporated in your description. E.g, you’re including your company logo: if you only describe what the logo looks like without explaining that the image is a logo, the alt text is missing context, and the viewer won’t understand its meaning. Also, if the image is linked, the alt text should describe what happens when the image is clicked.
Alt text for complex images like graphs, diagrams, and charts should include the key takeaways from the content at the very least. Consider what the graph is telling people who look at it and summarize that result instead of simply saying the image is a graph. If you have a lot of information in an image, you may want to have a text version of the information linked elsewhere that’s more in-depth than the brief alt text description.
Be concise and accurate with your descriptions
Alt text is meant to be no more than a few brief sentences, so it’s important to make each word count. Be concise, because when email clients only load alternative text instead of images, that description has to convince people to download the images. You have a better chance of persuading people if they understand quickly why the image is important.
It’s not necessary to include phrases like “this is an image of…” or “a picture of”, since software understands that alt text is meant to describe images and will provide that context if necessary. You can also limit your descriptions to only the most key elements of the image. This would mean focusing only on the parts of the image that are important to convey your message.
Practice describing images
The best way to learn how to write precise, accurate alternate text quickly is to practice. There are a few ways to do this, including finding some images, describing them on a separate piece of paper, and then asking someone to read it and tell you what the image’s purpose is. There are also resources to help you learn strategies for image description, including one that helps you describe graphs and diagrams and another with some examples of good alt text.
Mark decorative images
Some images in your emails might not be there to send a particular message; they’re only there to make the email look nice visually. Examples of decorative images would be simple backgrounds, borders, and other simple elements. If the image is purely there for decoration, you can mark it as decorative, so text-to-speech software knows to skip over it.
Your email client should have either a way to mark it as decorative (usually in the same place as the alt text field), or you can leave the alt text field blank. Check the documentation for your email provider to learn the specifics.
Test your emails
Once you’ve written your alt text and incorporated it into your email, it’s important to test it’s working properly. If it doesn’t work right, your email will look unprofessional at best, and at worst, may not send the message you’re trying to send.
A robust testing strategy includes testing how your email will look in multiple configurations. Each email client your recipients use may display the image descriptions differently or may not display them at all. Some may automatically download and display the images, some might have settings chosen by the user to display the alt text instead, and still others may automatically block all external content.
The only way to know for sure how your email is going to look in someone’s inbox is to simulate it. Email testing tools like Mailosaur help you test different email rendering across email clients, browsers, settings, and other variables so you can quickly and efficiently check that your emails will perform how you expect them to.
Email testing tools can help
Mailosaur offers email and SMS testing software tools that can help you create fast, effective tests to see if your alternative text is working, and test countless other aspects of your transactional messages so you know everything works as it should.
If you'd like to give it a go, book a demo with one of our experts, or dive straight in to your 14 day free trial.