EPUB Metadata Editor

This tool edits the bibliographic metadata stored inside an EPUB's package (OPF) file — the Dublin Core fields that e-readers, library catalogs, and storefronts read to identify a book. It is meant for the moment after a book is built or acquired but before it is shelved or shipped: correcting an author name that imported wrong, setting a publisher line, fixing a missing or incorrect language code, or pasting in a proper description blurb.

Concrete cases that genuinely fit: self-publishers preparing a file for Apple Books, Kobo, or Google Play who need the title and rights line to match their listing; librarians and archivists normalizing a shelf of EPUBs so titles and authors display consistently; teachers or students cleaning up classroom reading files whose metadata shows as 'Untitled' or 'Unknown Author' on a tablet. It pairs naturally with the EPUB Validator and the platform-specific checkers, which flag metadata problems this editor then fixes.

Because everything runs in your browser and, on this site, the file is not uploaded, it is also suited to unpublished manuscripts and rights-sensitive material. The book stays on your machine; closing the tab discards it.

The flow is: drop or select a .epub file, let it parse, edit the form, then click Save and download EPUB. On load the tool reads the OPF and pre-fills seven editable fields — Title (required), Author, Publisher, Language, Publication date, Rights/Copyright, and Description. You change what you need and leave the rest; on save it rewrites the matching Dublin Core elements (dc:title, dc:creator, dc:publisher, dc:language, dc:date, dc:rights, dc:description), repackages the ZIP with the correct application/epub+zip type, and hands you a new file named with an '-updated' suffix. Your original is left untouched.

Language expects a BCP 47 tag (for example en, en-US, fr, de) and date is a free-text field where an ISO form like 2024-01-15 is the safe choice. If a field was absent in the original file, the tool creates that element rather than failing. The Save button stays disabled until Title has a value.

What it does not do is as important: despite the tool's summary mentioning 'subject,' the editor does not expose or write subject/keyword tags, and it does not edit the book's identifier (ISBN/UUID), subtitle, series, or contributor roles. It does not touch cover images, chapters, or layout, does not convert to other formats, and does not validate that your language tag or date are well-formed.

DRM-protected files cannot be edited — the tool detects encryption and stops with a clear message rather than producing a broken file. It also only opens genuine EPUB ZIPs; a renamed or corrupt file will be rejected. There is a per-file size ceiling typical of browser-side processing, so very large illustrated EPUBs may be slow or refuse to load on low-memory devices.

The most common mistake is expecting a field that is not there. If you came to add subject keywords, a category code, or a fresh ISBN, this editor will not do it — those live in elements it does not write. A second pitfall is the Author field: it maps to a single dc:creator, so multi-author books or specific role/file-as ordering are not fully represented here.

Also note that values are written as plain text into existing elements; the tool does not strip stray HTML you paste into Description, normalize smart quotes, or de-duplicate metadata if the original OPF already had multiple title or creator entries. Garbage in is preserved as-is.

After downloading, open the '-updated.epub' in the actual target — your e-reader app, Calibre, or the same FormatOS EPUB Inspector/Validator — and confirm the title, author, publisher, language, date, rights, and description all show the values you entered, with correct accents and capitalization. Verify the language tag renders as a real locale and that the file still opens and paginates normally, since repackaging touches the whole archive.

If you are targeting a specific store, run the file back through the relevant checker (Kindle, Apple Books, or Kobo) to confirm your metadata changes did not leave a required field empty. Keep your original until you have confirmed the new file is sound; the tool intentionally writes a separate copy so you always have a fallback.

For anything official, financial, or legal — an ISBN-registered publication, a copyright/rights statement, or a contractual deliverable — treat this as a convenience step and verify manually. Confirm the rights line, publisher, and dates against your authoritative records or your registrar/distributor before publishing or submitting.