Alt text (alternative text) is a text description attached to an image that conveys its content to people who can't see it. In ebooks, missing or poor alt text is the single most common accessibility violation, and one of the leading causes of Amazon ranking suppression.
This guide covers everything you need to know about writing alt text for ebooks: the rules, the techniques, and the edge cases.
Why Alt Text Matters
For readers
Approximately 2.2 billion people worldwide have some form of vision impairment. Many of these readers use screen readers, software that reads digital content aloud. When a screen reader encounters an image without alt text, it either skips it entirely or reads the filename ("image_2847.jpg"), which is useless.
Good alt text makes your book's visual content accessible to these readers.
For your rankings
Amazon's KDP quality system checks for image alt text as part of its accessibility evaluation. Each image missing alt text adds to your book's risk score. A book with 10 images and zero alt text can accumulate enough violations to trigger suppression, reduced visibility in search results and recommendations.
For compliance
The European Accessibility Act (in effect since June 2025) requires alt text for all meaningful images in ebooks sold in the EU. This isn't optional, it's a legal requirement.
The Rules of Good Alt Text
Rule 1: Be Concise
Aim for under 125 characters when possible. Screen readers announce alt text as a single block, so long descriptions interrupt the reading flow. If an image requires a detailed explanation, use a figure caption instead and keep the alt text as a summary.
Too long: "A detailed bar chart showing the quarterly sales figures for the company's three main product lines, widgets, gadgets, and sprockets, from Q1 2024 through Q4 2025, with widgets showing the strongest growth at 45% year-over-year while gadgets declined 12%"
Better: "Bar chart: Widget sales grew 45% YoY while gadget sales declined 12%, Q1 2024 to Q4 2025"
Rule 2: Describe Content, Not Appearance
Tell the reader what the image communicates, not what it looks like at a technical level.
Poor: "A 400x300 pixel JPEG photograph with warm tones"
Good: "Author Margaret Atwood speaking at a podium during the 2024 Booker Prize ceremony"
Rule 3: Skip "Image of" or "Picture of"
Screen readers already announce that the element is an image. Starting with "Image of" creates redundancy: "Image: Image of a sunset." Just describe the content directly.
Poor: "Photo of a sunset over the ocean"
Good: "Sunset over the Pacific Ocean, viewed from the California coast"
Rule 4: Include Visible Text
If an image contains text (a sign, a book cover, a screenshot), include that text in the alt attribute. Screen readers can't read text embedded in images.
Example: "Book cover: 'The Great Gatsby' by F. Scott Fitzgerald, featuring art deco gold lettering on a dark blue background"
Rule 5: Use Empty Alt for Decorative Images
Decorative images, borders, spacers, ornamental dividers, don't convey meaningful content. Give them empty alt text (alt="") so screen readers skip them.
<!-- Decorative divider -->
<img src="images/divider.png" alt="" />
<!-- Meaningful image -->
<img src="images/diagram.png" alt="Cell division process showing mitosis phases" />
If you're unsure whether an image is decorative, ask yourself: "If I removed this image, would the reader miss any information?" If the answer is no, it's decorative.
Alt Text by Image Type
Different types of images require different approaches:
Book Covers
Describe the title, author, and key visual elements.
"Cover of 'Dune' by Frank Herbert: a vast desert landscape with two moons in an orange sky"
Photographs
Identify people, setting, and action. Include names if the person is relevant to the text.
"Marie Curie in her laboratory, 1912, examining a glass vial"
Charts and Graphs
State the chart type, what it measures, and the key takeaway.
"Line graph showing global temperature rise: +1.2C from 1880 to 2024, with sharp acceleration after 1980"
Diagrams and Illustrations
Describe the process or concept being illustrated.
"Flowchart of the publishing process: manuscript to editing to typesetting to printing to distribution"
Maps
Identify the region and what the map highlights.
"Map of Western Europe with EU member states highlighted in blue"
Screenshots
Describe the interface and the relevant content shown.
"KDP dashboard showing a book's quality warning status with an orange alert icon"
Equations and Formulas
If your book includes mathematical content, describe the equation in words or use MathML.
"Einstein's mass-energy equivalence equation: E equals m times c squared"
Common Mistakes
Generic descriptions. "A chart" or "An illustration" tells the reader nothing useful. Be specific about what the image shows.
Over-description. A 500-word alt text is worse than no alt text, it derails the reading experience. Summarize; don't narrate.
Repeating the caption. If a figure caption already describes the image, the alt text should add context, not duplicate the caption.
Forgetting decorative images. An EPUB with 50 images and 50 alt text descriptions sounds complete, but if 30 of those images are decorative and should have empty alt text, 30 of your descriptions are adding noise.
Using AI for Alt Text
AI vision models can generate alt text automatically by analyzing the image content. This can be a significant time-saver, especially for books with many images. However, AI-generated alt text should always be reviewed by a human.
Why? AI models can:
- Misidentify people or objects
- Miss the context that surrounding text provides
- Generate generic descriptions that don't serve the specific book's needs
- Get factual details wrong (especially for domain-specific images)
The best workflow combines AI efficiency with human judgment: let the AI generate a first draft, then review and edit each description. Rahatt's alt text feature does exactly this, it generates context-aware suggestions using the surrounding book text, then presents them for your review before applying.
How Many Images Need Alt Text?
Every image that conveys meaning needs alt text. For a typical novel with a cover and a few chapter illustrations, this might be 5-10 images. For a non-fiction book with charts, diagrams, and photographs, it could be 50+.
Each missing alt text adds to your accessibility risk score. On Amazon, the penalty is roughly -10 points per image (capped at -40), so even a few missing descriptions can move you from "Low Risk" to "Medium Risk" territory.
Checking Your Alt Text
After adding alt text, verify it by:
- Re-scanning your EPUB with an accessibility checker like DAISY Ace
- Listening with a screen reader (VoiceOver on Mac, NVDA on Windows)
- Reading each description out of context, does it make sense without seeing the image?
The third check is the most important. If your alt text only makes sense when you can see the image, it needs rewriting.