Looking for Problematic EPUB Files — Free Troubleshooting and Repair

[NurViewer]

Hi everyone,

We're the team behind NurViewer, and we're currently working on improving its EPUB reading, conversion and file-repair capabilities.

Real-world problem files are especially valuable for testing, so we'd really appreciate some help from fellow MobileRead members.

If you've encountered any of the following problems, we'd be happy to investigate and try to help free of charge:

- Calibre takes an unusually long time to convert an EPUB to PDF, or the conversion fails.
- An EPUB cannot be opened by your usual reader, or causes errors or crashes.
- An EPUB opens, but the layout is broken — missing text or images, incorrect page layout, misplaced illustrations, or other rendering problems.
- An EPUB appears damaged or has structural errors that are difficult to fix.

You don't need to send us the file immediately. Just describe the problem here, including the reader or conversion tool used, any error messages, and screenshots if available.

If we need the original file to investigate further, we can discuss a private way to share it.

A few notes:

1. Please don't share confidential, sensitive or personal content.
2. Only provide files you have the right or permission to share. Please don't upload copyrighted books to the forum.
3. Any files shared privately will be used only for the agreed investigation and repair. We won't publish or redistribute them, or share their contents in public examples, without your permission.
4. We can't guarantee every file can be repaired, but we'll do our best and explain what we find.

This is a free technical testing and assistance effort. No purchase or software installation is required.

Thanks in advance to anyone willing to share a difficult case or offer suggestions. Your help will be genuinely valuable to our development work!

[Doitsu]

It looks like you're trying to develop an app which already exists: epubsana
The author recently also released a test suite.

[Kayadelenium]

Thanks for the mention, Doitsu. Since my tools came up, here is where they stand, in case they help with what you are testing.

Most of my time right now goes into reading the EPUB specifications and turning them into test books. Each book in epub-test-books checks one rule, and I write the expected result from the specification before any validator runs on it. That has shown me bugs in epubveri, my own validator, that a shelf of real books never would have, and I fix them as they come up. It has also turned up places where epubcheck disagrees with the specification, and I report those on its issue tracker: 19 issues so far, five of them closed.

epubsana is the repair side. It takes the defects epubveri reports, proposes the ones that have exactly one correct fix, asks before each change, and writes the result to a new file, so the original is never touched. Some of what the test books uncover is now repaired automatically this way. What needs an editor's judgement, it leaves alone.

My time is limited, so the test books and epubveri come first. With what is left I fix bugs in epubsana, kepubverto (EPUB to Kobo KEPUB), imagoverto (image conversion), paginaverto (PDF and page images to a structured document) and epublift.

All of them are 100% free software, with their full source code public under the AGPL, and I will keep developing them in the open as my work and private life leave time. One of my goals is to build them in pure Rust, with no C libraries and no Java runtime. The test books themselves are CC BY 4.0, so anyone can copy them into their own test suite. If you want to help, try them on your own files and report what goes wrong. A book that breaks one of my tools is the most useful bug report I can get.