What image formats are supported in EPUB?

EPUB 2 and 3 both support JPEG, PNG, and GIF. EPUB 3 adds SVG support. WebP has limited e-reader support and should be avoided. For maximum compatibility, use JPEG for photos and PNG for diagrams and images requiring transparency.

What size should the cover image be for an EPUB?

Standard cover size is 1600x2400 pixels at a 2:3 aspect ratio. Amazon KDP requires a minimum of 1000x1600px. Apple Books requires at least 1400px on the short side. Larger images are fine but increase file size.

How do I add alt text to images in an EPUB?

Add an alt attribute to every img element. For informative images, describe what the image shows. For decorative images, use alt='' (empty string, not missing). For complex figures like charts, use aria-describedby pointing to a figcaption with a full description.

How large should images be in an EPUB file?

Keep individual body images under 200KB. Total EPUB file size should ideally stay under 10MB for comfortable loading on older devices. Compress JPEGs to quality 80 and run optipng or pngquant on PNGs before embedding. Use convert or mogrify to batch resize to max 1200px wide.

Can I use SVG images in an EPUB?

Yes, SVG is supported in EPUB 3. It's ideal for vector diagrams, icons, and graphics that need to scale cleanly across screen sizes. Reference SVG files via img src or embed inline in XHTML. SVG is not supported in EPUB 2.

EPUB Images: Formats, Compression, Alt Text, and Cover Best Practices

June 11, 2026 · 7 min read

Images in EPUBs require more care than in print or web. E-ink screens have different colour depths, memory limits vary by device, and accessibility requirements mandate alt text. Here's everything you need to know about handling images correctly in EPUB.

Supported Image Formats

Format	EPUB 2	EPUB 3	Use case
JPEG / JPG	Yes	Yes	Photos, screenshots, complex illustrations
PNG	Yes	Yes	Diagrams, charts, images requiring transparency
GIF	Yes	Yes	Simple graphics (avoid — large files)
SVG	No	Yes	Vector diagrams, icons, scalable graphics
WebP	No	Partial	Not recommended — poor reader support

Safe choice: JPEG for photos, PNG for diagrams. Avoid WebP — it's not widely supported by e-readers as of 2026.

Recommended Image Dimensions

E-readers vary in screen resolution. A practical rule:

Body images — max 1200px wide. Most e-ink screens are 600–1448px wide. Larger images are scaled down but waste memory.
Cover image — 1600×2400px (2:3 aspect ratio) at 72dpi is the standard. Amazon KDP requires at least 1000×1600px. Apple Books requires at least 1400px on the short side.
Full-page images — match the cover dimensions. Use a separate full-page spine item with the image filling the XHTML body.

Compression Before Embedding

Large images slow down EPUB loading and inflate file size. Compress before embedding:

# JPEG: recompress at quality 80 (good quality, ~50% smaller)
convert input.jpg -quality 80 output.jpg

# PNG: lossless compression
optipng -o5 image.png
# or
pngquant --quality 60-80 image.png

# Batch resize all JPEGs to max 1200px wide
mogrify -resize "1200>" -quality 80 *.jpg

Target: body images under 200KB each, total EPUB under 10MB for comfortable loading on older devices.

Alt Text for Accessibility

EPUB Accessibility 1.1 and WCAG 2.2 AA require meaningful alt text on all informative images. The alt attribute on <img> elements is the standard approach:

<!-- Informative image -->
<img src="images/figure1.jpg" alt="Bar chart showing conversion accuracy by document type: 98% for text-only PDFs, 91% for two-column, 87% for scanned."/>

<!-- Decorative image (empty alt, not null) -->
<img src="images/divider.png" alt="" role="presentation"/>

<!-- Complex image with extended description -->
<figure>
  <img src="images/circuit.png" alt="Circuit diagram — see description below" aria-describedby="fig1-desc"/>
  <figcaption id="fig1-desc">Full description: power supply connects to...</figcaption>
</figure>

Cover Image Setup

The cover image requires two declarations in EPUB: the manifest item and the cover-image property.

<!-- In content.opf manifest -->
<item id="cover-image" href="images/cover.jpg"
      media-type="image/jpeg" properties="cover-image"/>

<!-- Cover XHTML page (for the visual cover in the reading flow) -->
<item id="cover" href="cover.xhtml" media-type="application/xhtml+xml"/>

The cover.xhtml page should contain only the image, sized to fill the viewport:

<body style="margin:0;padding:0;">
  <img src="images/cover.jpg" alt="Book cover" style="width:100%;height:100%;object-fit:contain;"/>
</body>

SVG Images in EPUB 3

SVG is supported in EPUB 3 and works well for diagrams and icons that need to scale perfectly. Embed via <img src="diagram.svg"> or include SVG inline in the XHTML. Inline SVG gives full CSS styling control but inflates individual content files. External SVG files referenced via img are cleaner for large diagrams.

Images from PDF Conversion

When converting a PDF to EPUB, images are automatically extracted and embedded. toolkit.bot preserves image quality, adds alt text where possible from PDF metadata, and optimises file sizes. Complex figures (charts, tables rendered as images) include descriptive alt text generated from surrounding context.

Convert your PDF to EPUB free →