Definition
A fallback image in email is an alternative visual or treatment that displays when the primary image cannot load — for example, because the client blocks images by default or the host image request fails. It ensures the email still makes sense without the main graphic.
Because many clients block images until the recipient permits them, relying on a single image leaves parts of the email invisible. A fallback — a background colour, an alt text, or a simple substitute graphic — keeps the layout coherent and the message readable regardless of image settings.
Why Images Fail to Show
| Cause | Where It Happens |
|---|---|
| Images blocked | Many clients block by default |
| Image request fails | Broken URL or host downtime |
| Lazy loading | Image loads only after interaction |
| Offline reading | Recipient opens without connection |
A fallback covers these gaps.
Fallback Approaches
| Approach | Purpose |
|---|---|
| Alt text | Describes the image when unseen |
| Background colour | Keeps the block recognisable |
| Text-based CTA | Works even with images off |
| Substituted graphic | A simpler, reliably loaded visual |
Each keeps the email understandable.
How to Add Fallbacks
- Write meaningful alt text: Describe content for hidden images.
- Set a background colour: Keep the container visually intact.
- Design without relying on images: Ensure text carries the message.
- Test with images off: Confirm the email still reads correctly.
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.
Alt Text
Alt text is the written alternative to an image in an email, displayed when images are blocked, slow to load, or consumed by screen readers.
Frequently Asked Questions
A fallback image is an alternative graphic or treatment shown when the primary image cannot load, such as when the client blocks images. It keeps the email presentable and readable without the main visual.
Because many email clients block images by default until the recipient allows them. Without a fallback, images-only designs turn invisible and the message is lost. Alt text, colour and text-based CTAs keep the email working with images off.
Meaningful alt text that describes the image's content, a background colour to keep the block recognisable, and a text-based call to action so users with blocked images can still act. Test the email with images disabled to confirm readability.
Send the email to yourself with images blocked in your client or provider, and confirm texts, CTAs and layout still communicate the message. This mirrors the common recipient experience where images do not load on the first open.