How do I edit EPUB metadata in Calibre?

Open Calibre, add your .epub file, click the book and press E (Edit metadata). Edit title, author, series, language, ISBN, description, and cover image. Click OK. Then right-click → Save to disk → Save only EPUB format to disk to export the updated file. The changes are written to the OPF manifest inside the EPUB.

How do I change the cover image of an EPUB?

In Calibre's metadata editor (select book → press E), click Browse next to the cover preview and select a JPEG or PNG. Recommended size: 1600×2400px for most platforms. Click OK and save to disk. Calibre writes the cover into the EPUB's manifest with the correct cover-image property declaration. KDP recommends 2560×1600px minimum.

Where is EPUB metadata stored?

EPUB metadata is stored in the content.opf file inside the .epub ZIP container. The OPF file contains Dublin Core elements: dc:title, dc:creator (author), dc:language, dc:identifier (ISBN/UUID), dc:publisher, dc:date, and dc:description. The cover image is referenced in the manifest with properties='cover-image'. Calibre reads and writes all these fields through its metadata editor.

What EPUB metadata is required for KDP and Kobo?

KDP requires: title, at least one author, language (ISO 639-1 code), a unique identifier (ISBN or UUID), and a valid EPUB structure. Kobo Writing Life requires the same plus a cover image embedded in the EPUB. Apple Books Connect requires title, author, language, and a cover at least 1400×1400px. All platforms require EPUB 3 format for new uploads.

How to Edit EPUB Metadata — Title, Author, Cover, and ISBN (Calibre Guide)

EPUB metadata is the information that reading apps and publishing platforms display: title, author name, series, cover image, ISBN, and language. Wrong metadata shows up in your Kindle library as "Unknown" author or a missing cover. Here's how to fix it in Calibre — free, 5 minutes.

What EPUB Metadata Includes

Title — the book's display name in library apps
Author(s) — primary author and contributors (editor, translator)
Series / Series number — for books in a sequence (Calibre-specific; also standard in EPUB 3)
Publisher — publishing house or self-publisher name
Date published — year, used for sorting in some apps
Language — ISO 639-1 code (en, fr, de…); required for WCAG and EAA compliance
ISBN / Identifiers — ISBN-13, ASIN, DOI, or custom identifiers
Description — book blurb shown in library apps and on publishing platforms
Cover image — the 1600×2400px JPEG displayed in library views

Step-by-Step: Edit Metadata in Calibre

Calibre is the standard free tool for EPUB metadata editing. Download from calibre-ebook.com.

Open Calibre. Click Add books and select your .epub file.
Click the book in the library, then click the Edit metadata button (or press E).
Edit any fields: Title, Author(s), Publisher, Date, Series, Language, ISBN, and Description.
To change the cover image: click Browse next to the cover preview → select a JPEG or PNG (recommended: 1600×2400px, 300 DPI).
Click OK to save.
Right-click the book → Save to disk → Save only EPUB format to disk → choose a folder.

The saved .epub now contains updated metadata embedded in the OPF file and updated cover image. Upload this file to KDP, Kobo Writing Life, Apple Books Connect, or any other platform.

Edit Metadata Directly in the OPF File

EPUB metadata lives in the content.opf file inside the .epub ZIP container. Advanced users can edit it directly:

# Unzip the EPUB
unzip book.epub -d book-contents/

# Edit the OPF file
nano book-contents/EPUB/content.opf

# Repack to EPUB (must use mimetype as first file, uncompressed)
cd book-contents
zip -X ../book-new.epub mimetype
zip -rg ../book-new.epub . -x mimetype

Cover Image Requirements by Platform

Platform	Recommended size	Format
Amazon KDP	2560×1600px min	JPEG
Kobo Writing Life	1600×2400px	JPEG or PNG
Apple Books Connect	1400×1400px min	JPEG or PNG
Draft2Digital	1600×2400px	JPEG or PNG

Common Metadata Errors and Fixes

"Unknown" author on Kindle: Author field is blank or contains "Unknown" in the OPF. Edit in Calibre and re-upload to KDP.
Missing cover on Kobo: Cover image is not declared in the OPF manifest with properties="cover-image". Use Calibre's metadata editor to set a new cover, which handles the OPF declaration automatically.
Wrong language in EPUB: Edit the <dc:language> element in the OPF. Required for EAA/WCAG 3.1.1 compliance. Calibre's Language field writes this automatically.
KDP rejects the EPUB: Often caused by a missing or invalid <dc:identifier>. Add any unique ID (can be a UUID) in Calibre's Ids field.

Coming From a PDF?

If you're converting a PDF to EPUB for publishing, use toolkit.bot/pdf2epub to produce the EPUB, then edit the metadata in Calibre before uploading to your distribution platform. toolkit.bot extracts document structure; Calibre adds the publishing metadata and cover image.

Need a clean EPUB from your PDF manuscript? Convert in 30 seconds — then add your metadata in Calibre.

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