Definition
Alt text, short for alternative text, is a written description embedded in an image tag within HTML email. It serves three primary purposes: it describes images to visually impaired subscribers using screen readers, it displays in place of images when image blocking is active, and it gives context to spam filters scanning the content of the email.
Image blocking is still common. Some clients block images by default, and recipients on slow connections may not see images immediately. Without alt text, those subscribers see blank spaces where the message should be. With clear, descriptive alt text, the email still communicates its purpose even in a purely text-based state.
Good alt text is concise, descriptive and functional. It should describe what the image shows and, if the image is a button or link, what action it triggers. Decorative images, such as background shapes or dividers, should use empty alt attributes so screen readers skip them. Marketing images should avoid repeating the subject line or adding redundant phrases like 'image of.'
Best Practices
- Keep alt text under 125 characters for screen-reader compatibility.
- Use empty alt attributes for decorative images to avoid screen-reader noise.
- Write action-oriented alt text for linked images, such as 'Shop the summer sale' instead of 'Summer banner.'
- Test your email with images disabled to verify the message still makes sense.
- Avoid keyword stuffing in alt text; focus on clarity and accessibility.
Related Glossary Terms
Above the Fold in Email
Above the fold in email refers to the content visible to a recipient before they scroll, a critical area for first impressions and primary calls to action.
Abuse Complaint
An abuse complaint is a report from a recipient who marks an email as spam, which negatively affects sender reputation and deliverability.
Accessible CTA (Email)
An accessible CTA is a button or link coded with sufficient colour contrast, visible focus states, descriptive screen-reader text, and a minimum touch target of 44×44 pixels.
Adaptive Design
Adaptive design in email uses predefined layouts that adjust to specific device or client widths, rather than fluidly resizing to every possible screen.
AI-Generated Content in Email
AI-generated content in email is copy, images, code or subject lines produced by artificial intelligence tools to speed up campaign production and testing.
AOL Mail for Email Marketers
AOL Mail is a legacy email provider with specific deliverability requirements and rendering quirks, now operating as part of the Yahoo+AOL network under shared infrastructure.
Frequently Asked Questions
Yes. Alt text is a core requirement of WCAG and makes emails usable for screen-reader users and recipients with image blocking enabled.
Most modern clients show alt text, but formatting varies. Outlook has limitations, and some mobile clients strip styling. Always test across major clients.
Indirectly. Alt text adds textual content, which helps spam filters understand the email. However, keyword stuffing or misleading alt text can hurt deliverability.
Alt text describes the image for accessibility and displays when images are blocked. Title text appears as a tooltip on hover and is not a substitute for alt text.
Yes. Logo alt text should include the brand name, such as 'Email Calculator logo,' so the brand is identifiable even with images disabled.