EPUB Validator
Free tool — no sign-up, nothing uploaded
Free EPUB Validator: Run EPUBCheck Online in Your Browser
Check your EPUB against the EPUBCheck rules that stores such as Apple Books, Kobo and IngramSpark use. You'll see every error and warning with its file and line number, your book's metadata, and whether the file shows signs of automated conversion. Your EPUB is checked inside your browser and never uploaded.
Choose an EPUB file
Private: your EPUB is checked inside your browser. It is never uploaded, and we never see or store it.
Your results
Powered by epubcheck-ts 0.7.0, an open-source port of the W3C EPUBCheck (licences). It agrees with the official EPUBCheck on whether a file passes for about 97% of test files; full checks of page code against the XHTML schema are not included.
How to Validate an EPUB in 4 Steps
- Choose your EPUB. Drop the file on the box above or click Choose EPUB file. Tick Also check accessibility if you sell in the EU or want your book to be accessible to more readers.
- Read the result. Errors must be fixed before stores will accept the file. Warnings point to likely display problems and are worth fixing. Info notes are for your information.
- Open Metadata and How this EPUB was made. They show missing book details, and whether the file was produced by an automated converter.
- Fix, then check again. Re-run the file after every change until it passes. If you’d rather we fixed it, download the report and attach it to your quote request.
What Your EPUBCheck Results Mean
Every result leads to one of three next steps. The validator shows the one that applies to your file under What to do next.
Errors found
Apple Books, Kobo, Google Play and IngramSpark reject EPUB files with EPUBCheck errors, and errors are a common cause of KDP conversion problems. Every error has to be fixed, and the file checked again.
Passed, but machine-converted
A file made with Calibre, Word or an online converter can pass EPUBCheck and still be full of messy code that displays differently from device to device. For these files we recommend formatting the book from scratch.
Metadata gaps
A file can pass EPUBCheck with only a title, language and identifier. Kindle and other reading apps also use the author, cover, table of contents, start reading location and accessibility details, so the report lists anything missing.
Why Passing EPUBCheck Isn't the Whole Story
EPUBCheck answers one question: does the file follow the EPUB rules? It doesn’t check whether the book is well formatted. A file can pass with no errors and still have:
- Styling repeated on every paragraph instead of in one stylesheet, which overrides the reader’s font and size settings
- Fixed font sizes that don’t respond to the reader’s text-size setting
- Spaces and blank lines used for layout, which shift or leave gaps on different screen sizes
- Leftover word-processor code, such as empty tags and Word styles, that makes fonts and indents inconsistent
These problems come from automated conversion: exporting from Word, Google Docs or Pages, or converting with Calibre or an online converter. Fixing the EPUBCheck errors in such a file makes it acceptable to stores, but it doesn’t clean up the formatting underneath.
If your book was formatted with an automated tool, we highly recommend formatting it from scratch. We’ve hand-coded every eBook since 2008, in clean HTML and CSS, without conversion software. The validator’s How this EPUB was made section shows whether your file has these signs, and how many.
Whatever the result, preview your book in Kindle Previewer and in Apple Books on a phone and a tablet before you publish.
Check Your EPUB Metadata Too
Metadata is the information inside your EPUB about the book itself: title, author, language, identifier or ISBN, publisher, cover and accessibility, plus the table of contents, NCX and start reading location that Kindle Previewer lists under Book Information. Reading apps use it for the library, the cover thumbnail, navigation and where the book opens. EPUBCheck only requires a few of these, so a file can pass with most of them missing.
The validator report includes a metadata summary. For a quick check on its own, which gives results in about a second, use our free EPUB Metadata Checker.
How This EPUB Validator Works
The validator uses epubcheck-ts, an open-source port of the W3C’s official EPUBCheck that runs in a web browser. Your file is read and checked on your own computer. It’s never uploaded, so it’s safe to check unpublished manuscripts.
On its developers’ test suite of 758 files, it reaches the same pass or fail verdict as the official EPUBCheck about 97% of the time. The main gap is that it doesn’t fully check page code against the XHTML schema, and its checks of images and audio are basic. Use it to find and fix problems; for a final check before an important release, the official Java EPUBCheck remains the reference.
Frequently Asked Questions
Yes. There’s no sign-up and no email required, and you can check as many files as you like.
No. The file is read and checked inside your browser. It never reaches our server, and we can’t see it.
Errors break the EPUB rules, and stores such as Apple Books, Kobo, Google Play and IngramSpark reject files that have them. Warnings point to things that often cause display problems; fix them where you can. Info notes are for your information and need no action.
KDP accepts EPUB files and converts them for Kindle. Passing EPUBCheck removes the most common causes of conversion problems, but KDP runs its own checks, so preview the book in Kindle Previewer before you publish.
EPUBCheck checks the rules, not the formatting. Files made by automated tools often pass and still contain inline styles, fixed font sizes and leftover word-processor code that display differently on each device. The report’s How this EPUB was made section shows whether your file has these signs. If it does, we recommend formatting the book from scratch.
If the file was built carefully and has a handful of errors, a repair is the quickest fix. If it was converted with Word, Calibre or an online converter, fixing the errors makes it acceptable to stores but leaves the messy formatting in place, so reformatting from scratch is usually the better value. Send us the report and we’ll recommend one or the other.
Yes. Our EPUB Validation & Repair service fixes every error in the report, completes missing metadata, and re-checks the file with EPUBCheck before delivery, within 72 hours.
No. It’s epubcheck-ts, an open-source port of the official W3C EPUBCheck that runs in your browser. It matches the official tool’s pass or fail verdict on about 97% of its developers’ test files. Ebookifi isn’t affiliated with the W3C or with any store.
Want It Fixed, or Formatted Properly from Scratch?
We repair EPUB files by hand, or rebuild them in clean, hand-coded HTML and CSS, and re-check them before delivery.