How do I add a cover image to an EPUB?

In Calibre: select the book, press E to open metadata editor, click the cover area, click Browse to select a JPEG or PNG file, click OK. Calibre embeds the image and updates the OPF cover reference automatically. In Sigil: add the image to Images/, update the OPF manifest with properties='cover-image', add a cover meta element, and create a cover.xhtml file that displays it.

What size should an EPUB cover image be?

The widely accepted standard is 1600×2560 pixels (6:9 portrait aspect ratio) as JPEG. KDP recommends 2560×1600 px minimum (confusingly listed as width×height). Apple Books requires at least 1400 px on the shortest side. Kobo Writing Life minimum is 800×1000 px. Using 1600×2560 px at 72 DPI satisfies all major platforms.

Why does my EPUB cover not show on Kindle?

Common causes: missing properties='cover-image' in the OPF manifest item (EPUB 3 requirement), missing in OPF metadata (EPUB 2 compatibility for older Kindles), cover image larger than 127 KB (Kindle limit for older models — compress the JPEG), or the cover XHTML file not listed first in the OPF spine.

Can I use PNG for an EPUB cover image?

Yes — EPUB 3 supports both JPEG and PNG cover images. However, JPEG is recommended for photographs (smaller file size at equivalent quality) and PNG is better for covers with text or sharp graphics. For KDP specifically, JPEG is preferred. Keep the cover file under 5 MB to ensure fast loading on all devices.

How to Add or Change the Cover Image in an EPUB

A cover image is required by KDP, Kobo, and Apple Books, and it displays on every e-reader's library shelf. Here's how to add or replace a cover in any EPUB using Calibre and Sigil.

Method 1: Calibre Metadata Editor (Easiest)

For most cases, Calibre's metadata editor is the fastest way to set or replace a cover:

Select the book in Calibre's library.
Press E (or right-click → Edit metadata individually).
In the metadata dialog, click the cover image area on the right.
Click Browse to select a new image file (JPEG or PNG).
Click OK. Calibre embeds the image as the EPUB cover.

This updates both the cover image file in the EPUB and the OPF cover metadata reference. It's the recommended approach for quick cover updates.

Method 2: Sigil (Full Control)

Sigil lets you control exactly how the cover is embedded — useful if Calibre's output doesn't satisfy validator requirements:

Open the EPUB in Sigil.
In the Book Browser, right-click Images/ → Add Existing Files. Select your cover JPEG.

Open the OPF file (content.opf) in Code View. In the <manifest>, confirm the image has an entry:

<item id="cover-image" href="Images/cover.jpg" media-type="image/jpeg" properties="cover-image"/>

In the <metadata> section, add or update the cover reference:
```
<meta name="cover" content="cover-image"/>
```
Create or update the cover HTML page (cover.xhtml) that displays the image for readers that show a cover page.
Save and validate with EPUBCheck.

Cover Image Requirements by Platform

Platform	Minimum Size	Recommended Size	Format
Amazon KDP	1000 × 625 px	2560 × 1600 px	JPEG
Apple Books	1400 px on shortest side	2500 × 1563 px	JPEG or PNG
Kobo Writing Life	800 × 1000 px	1600 × 2400 px	JPEG or PNG
Draft2Digital	1600 × 2400 px	2400 × 3600 px	JPEG or PNG
Smashwords	1600 × 2400 px	2400 × 3600 px	JPEG or PNG

Use a 6:9 aspect ratio (portrait) as the standard. KDP's 1600×2560 px at 72 DPI is widely accepted across all platforms.

The Cover HTML Page

Most EPUB readers display a cover page when the book is opened. This requires a separate XHTML file (cover.xhtml) that displays the cover image full-page:

<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>Cover</title>
<style>
  body { margin: 0; padding: 0; }
  img { max-width: 100%; height: auto; display: block; }
</style>
</head>
<body>
  <img src="../Images/cover.jpg" alt="Cover"/>
</body>
</html>

Reference this file first in the OPF <spine> so it appears as the opening page.

Why the Cover Shows as Blank in Some Readers

If the cover shows in Calibre but not on the Kindle or Kobo device:

The OPF manifest entry is missing the properties="cover-image" attribute (EPUB 3).
The <meta name="cover"> element is missing (EPUB 2 compatibility).
The cover image file size is too large — Kindle has a 127 KB limit per image for older models.
The cover XHTML file is not listed first in the spine.

Converting a PDF to EPUB? toolkit.bot generates EPUBs with properly embedded cover metadata.

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