Which metadata fields can I edit?

Title, author, publisher, description, language, publication date, and cover image. Epublys writes these directly into the OPF file, so any reader or store that checks OPF metadata will see the updated values.

Will editing metadata break the EPUB?

No, if done through the editor. The tool writes valid XML to the OPF and does not touch any other files. If you edit the OPF by hand, malformed XML can break the package — always run the validator afterward to confirm.

Does the metadata editor upload my file?

Yes — it is sent over HTTPS to a Cloudflare Worker, where the metadata is edited in memory and the updated file is returned. It is never written to disk or stored: the in-memory copy is discarded the moment the response is sent. (The Epublys reader is the only fully in-browser tool; the editing tools process server-side.)

Why does my reader still show the old title after I edited it?

Most e-readers cache metadata at import time. Delete the book from your device and re-add the updated EPUB — the new title will appear. Calibre also caches internally; right-click → Edit metadata → apply from file to refresh.

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How to Edit EPUB Metadata

How to Edit EPUB Metadata

Edit EPUB Metadata →

EPUB metadata lives in a file called content.opf (or package.opf) inside the EPUB ZIP. It controls the title shown in your reader's library, the author name used for alphabetical sorting, the cover thumbnail, the dictionary language, and the blurb displayed in store listings. If any of it is wrong or missing, books end up under "Unknown Author," covers don't display, and store submissions get flagged.

What Each Field Actually Does

Title (dc:title) — Shown in library lists and in PDF document properties if you convert. Use the full canonical title; subtitle can follow after a colon.
Author (dc:creator) — The display name. Most readers sort by last name, but EPUB stores the full name. Use the file-as attribute (file-as="Orwell, George") to control sort order separately from display name.
Language (dc:language) — ISO 639 code: en, fr, de, zh. Readers use this to pick the hyphenation dictionary, spellcheck language, and TTS voice. Wrong or missing codes cause layout problems in RTL languages (Arabic, Hebrew).
Description (dc:description) — The blurb. Displayed in store listings and in the book-details panel of most readers. EPUB 3 supports HTML markup here, though reader rendering varies.
Identifier (dc:identifier) — A unique ID for the book. Use an ISBN for publishing, any unique string for personal use. Some platforms require this to be non-empty.
Cover image — A JPEG or PNG in the manifest flagged with the cover-image property. Should be at least 600px wide; 1200×1800px (2:3 ratio) is the standard for store thumbnails.
Subject/Genre (dc:subject) — Category tags used by stores for browse and recommendations. Multiple entries are fine. BISAC codes are the professional standard.

Edit Metadata: Epublys

Open the EPUB Metadata Editor
Upload your EPUB — existing metadata loads automatically from the OPF file
Edit fields and optionally upload a new cover image
Click Save Changes and download

Only the OPF metadata block is modified — chapter content and structure are untouched. Up to 10MB free; Pro handles up to 100MB.

Edit Metadata: Calibre

Right-click your book in Calibre → Edit metadata individually. Calibre also has "Download metadata" — it can look up covers, descriptions, and ISBNs from Amazon and Goodreads automatically, which is useful for cleaning up large collections. See the Calibre vs Epublys comparison.

Edit Metadata: Direct OPF Edit

Rename book.epub to book.zip, unzip, open the .opf file in any text editor, edit the <metadata> block, rezip, rename back to .epub. Fastest if you're comfortable with XML and only need to change one or two fields. Always validate after.

Why It Matters for Stores

Amazon KDP, Kobo Writing Life, and Draft2Digital pull metadata directly from the EPUB on upload. Wrong author names, missing ISBNs, or empty descriptions get flagged in the submission review. Getting it right before uploading saves a resubmission cycle. For personal libraries in Calibre or Plex, accurate metadata enables search by author, sorting by series, and automatic cover art matching.

Merge EPUB files — fix metadata after merging
Reduce EPUB file size — compress an oversized cover image
Validate your EPUB after editing metadata

Try it now — free

Edit EPUB metadata online. Change title, author, description, language, publisher. Free ebook metadata editor - no software needed.