Open your library and see three books titled "Untitled" by "Unknown Author" with no covers — that is what missing metadata looks like. EPUB metadata is the identity card of a book: the title and author your library displays, the language your reader picks for hyphenation, the ISBN stores use to match the edition, and the description that tells you what the book is when you've forgotten.
Editing it is one of the easiest and highest-value fixes in ebook management. This guide covers the fast way (a dedicated metadata editor), the thorough way (inside a full editor), and the batch way (Calibre), plus what each metadata field actually does.
Where EPUB Metadata Lives
Every EPUB carries its metadata in the package file (.opf) at the heart of the book — a small XML file listing the title, creator, language, identifier and other fields, plus the manifest of all files in the book.
You almost never need to open that file directly, but knowing it exists explains two everyday mysteries:
- Why "renaming the file" never works — the filename is not the title; the title inside the OPF is
- Why some books show odd library entries — whatever tool created the book wrote sloppy metadata into the OPF, and every reader since has faithfully displayed it
The Metadata Fields That Matter
| Field | What it does | Common problem |
|---|---|---|
| Title | Displayed everywhere: library, store, TOC headers | "Untitled", working titles, ALL CAPS |
| Author (creator) | Library sorting and display | "Unknown Author", "Last, First" inconsistencies |
| Language | Hyphenation, dictionary, font selection | Missing or wrong language breaks lookup |
| Identifier (ISBN) | Unique edition ID for stores and citation | Missing on self-made books; fake ISBNs |
| Description | The blurb in library apps and stores | Empty on converted files |
| Publisher & date | Edition information | Wrong decade from bad conversions |
| Cover | Declared in the same file — see the cover guide | Missing or broken declaration |
If a book looks wrong in your library, one of these fields is the reason — and each takes seconds to fix.
Method 1: Dedicated Metadata Editor (Fastest)
For pure metadata fixes — no text editing, no restructuring — a single-purpose tool is the cleanest path. The free EPUB metadata editor does exactly this:
- Drop in the
.epubfile. - Edit the fields on one screen: title, author, language, ISBN, description.
- Download the corrected book.
The tool rewrites the package file with clean declarations and leaves the content untouched. It runs entirely in your browser, so the file stays on your device — the right default for unpublished or personal material.
This is the method to reach for when the book itself is fine and only its "identity card" is wrong.
Method 2: Metadata Inside a Full Editor
When the metadata fix is part of a bigger cleanup — the book also needs text edits, a new cover, or a rebuilt TOC — do it all in one pass with the online EPUB editor:
- Open the book; the metadata panel sits alongside the chapter list.
- Update title, author, language, ISBN and description in one form.
- Replace the cover, fix text, reorder chapters as needed.
- Export once — all changes land in the same clean package.
The full editor is also the right tool when metadata and structure problems are tangled together: a book that shows the wrong title and has a broken TOC usually got both from the same bad export, and fixing them together avoids exporting twice.
Method 3: Calibre for Batch Metadata
Managing a library of hundreds? Calibre's strength is bulk operations:
- Select many books (or a whole collection) in the library view.
- Open bulk metadata edit.
- Apply changes across the selection — normalize author names to one format, fill a publisher, set languages.
The tradeoffs: Calibre is a desktop application you install and keep updated, and its metadata edits live in the Calibre library until you convert or export — you need to push the changes back into the EPUB files themselves if you use them elsewhere.
For one book, a browser tool wins on speed. For fifty, Calibre wins on scale.
Metadata Editing for Publishing
If the book is going to a store or distributor, metadata stops being cosmetic and becomes product listing:
- ISBN must match the edition exactly — the print ISBN does not cover the ebook
- Title should match the cover art and copyright page — reviewers and stores flag mismatches
- Description is your sales copy — plain text, front-loaded first sentence
- Language field drives eligibility for language-specific categories
- Validate before upload — stores reject books with malformed metadata; a quick pass with the EPUB checker catches what a store would
Why "Unknown Author" Keeps Coming Back
A frustrating pattern: you fix the author name, and after the next sync the old value returns. The cause is almost always one of:
- The fix was made to a copy, and your library re-imported the original file from another folder or cloud sync
- The reader cached the old metadata — delete the book from the device fully, then re-send the corrected file
- Calibre's library metadata overrode the file — edit in Calibre or let Calibre write back, not both half-way
Fix the source file, keep one canonical copy, and the problem stays fixed.
Frequently Asked Questions
Can I edit EPUB metadata without Calibre? Yes — a browser-based EPUB metadata editor changes title, author, ISBN and more without installing anything, and works on any OS.
Does editing metadata change the book content? No. Metadata editing rewrites only the package file describing the book; chapters, styles and images are untouched. Reading position may reset on some devices because the file changed.
How do I add an ISBN to a self-made EPUB? Enter it in the identifier field of any metadata editor. If you plan to sell the book, buy an ISBN from your local agency first — made-up numbers cause listing rejections. Personal library books can leave the field empty or use a UUID-style identifier.
Why does my reader show the old title after I fixed it? Reader apps cache metadata aggressively. Remove the book from the device completely, re-send the corrected EPUB, and restart the reader if needed.
Fix Your Library Now
The two-minute version: open the EPUB metadata editor, drop in the offending book, fill in the real title and author, download. Your library will thank you — and if the book needs deeper surgery, the EPUB editor is one click away.