Inspect
EPUB Inspector
Drop an EPUB to see what is inside it without opening it in a reader. The inspector reads the package file (OPF) and shows the book's metadata, a structure checklist, the table of contents, the reading order, the stylesheets, and every file in the archive sorted by size. Use it to understand a book before you convert, edit, or submit it to a store.
Written by Jay Sudha · Published · Last updated
Input formats
Output formats
Common uses
- Check what metadata an EPUB contains before editing
- Inspect the file structure before submitting to a publisher
- Find out why an EPUB is large by seeing which files take the most space
- Check that the table of contents and reading order match the book's chapters
Limitations
- DRM-protected EPUBs are refused, because their contents are encrypted. Font obfuscation, which some publishers use to protect embedded fonts, is not DRM and does not block inspection.
- It reads and reports only; to check a book against the EPUB rules in depth, use the EPUB Validator.
- Very large EPUBs (over 100 MB) may be slow to open in the browser, because every file is unpacked and measured.
Your e-book files, handled privately
This tool runs entirely in your browser. On this site, your files are not uploaded to a server. This tool does not remove DRM or bypass copyright protection. Only upload files you own or have permission to process.
When opening the EPUB's internals helps
EPUB Inspector is a read-only look inside an EPUB file. It unpacks the ZIP container in your browser and shows what a reading app normally hides: the Dublin Core metadata (title, author, publisher, language, date, identifier, rights and subjects), the table of contents, the reading order, the stylesheets, and every file in the archive sorted by size. Nothing is changed and nothing is downloaded.
It answers questions like "why does the table of contents look wrong" or "why is this file so big" before you resubmit, and confirms an export actually has a cover, a declared language and a sensible reading order.
Drop a file, read the report
Drag a file in or choose one, then read. There is no upload step: the EPUB is parsed with an in-browser ZIP reader and XML parser, so the file does not leave the tab. Big books take longer to open, because every file is unpacked and measured for the size list.
Supported input is a standard .epub (a ZIP container with a mimetype file, META-INF/container.xml and an OPF package). Both EPUB 2 and EPUB 3 are read: the table of contents comes from the EPUB 3 navigation document when there is one, otherwise from the EPUB 2 NCX. The report has the metadata; four counts (total size, content files, images and table-of-contents entries); a structure checklist; the table of contents; the reading order, with pages outside the linear order marked; the stylesheets with their sizes; every file by size; and a list of issues such as a missing title or language, an absent cover, or manifest files that are not in the archive.
What it does not do: it does not edit, repair, repack, convert or export anything, and it does not render pages. A book locked with DRM (Adobe, Apple, Readium LCP and similar) is refused rather than inspected; font obfuscation, which only scrambles embedded fonts, is not DRM and does not stop the report. For editing metadata or adding a cover, use the separate FormatOS tools.
Where the readings can mislead
The checklist and issue list flag common problems, but this is an inspection, not validation. The inspector does not check that XHTML pages are well-formed, that the identifier and modified date are valid, or that the mimetype file comes first in the ZIP; the EPUB Validator does, and even it covers only the rules EPUBCheck most often fails books on. Treat a clean report here as a description of the file, not a verdict.
A few specifics trip people up. The Content files count is every HTML or XHTML file in the manifest, which includes the cover page, the navigation document and chapters split across several files, so it rarely equals the number of chapters. The table of contents view shows the first 50 entries and the reading order the first 100 pages. Cover detection looks for the EPUB 3 cover-image property and the EPUB 2 cover meta; a cover that is only shown on a page, without being marked, is reported as missing even though a reader may display it.
A DRM-protected, renamed or damaged file gets a clear refusal rather than a partial report.
Confirming what the report tells you
Start with the metadata and the checklist: confirm the title, author and language read correctly and that the cover and table of contents pass. Then read the issue list, which names missing files by path.
Use the file list to sanity-check size: if one image dominates the total, that is your compression target, and if a stylesheet or font you expected is absent, the styling may be broken. Compare the table of contents and the reading order against the book's real chapter list to confirm the order and labels.
Where compliance matters, run EPUBCheck and the target store's tools too; the inspector describes the file, it does not certify it.
Frequently asked questions
No. The inspector only reads the file. Nothing is changed or uploaded.
The OPF (Open Packaging Format) file is the main descriptor inside an EPUB. It lists all the book's files, metadata, and reading order.
The spine defines the reading order of chapters inside an EPUB. Spine items are the HTML files that make up the book content, listed in the order a reading app will display them.
It counts every HTML or XHTML file in the manifest. That includes the cover page, title page and navigation document, and a chapter split across several files counts once per file. Compare the table of contents with your chapter list instead.
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Tool last reviewed: September 27, 2026 · Report a problem