Kobo Workbench: browser-based EPUB to KEPUB conversion with before-and-after checks

[KoboWorkbench]

Hi everyone,

I'm the maker of Kobo Workbench, a free browser tool for converting DRM-free EPUBs to KEPUB and checking the files before and after conversion.

https://kobo-workbench.pages.dev/

The workflow is:

- Check the original EPUB for missing files, reading-order issues and broken internal links.
- Convert it using Patrick Gaskin's kepubify engine.
- Check the output and compare reading-order text, original cover bytes, and selected table-of-contents and footnote targets.
- Download the .kepub.epub file and a JSON report.

The ebook files are processed locally in your browser. No account or installation is needed. The current limit is 50 MiB per book.

There are two built-in samples: a healthy EPUB and one with a broken contents link, so you can explore the report without using your own books.

These are limited file-level checks. They do not replace full EPUBCheck validation or testing the result on a Kobo. Kobo Workbench is an independent project and is not affiliated with Rakuten Kobo or the kepubify project.

I'd appreciate feedback from people who sideload books: does the report help you decide what to check next, and which messages need a clearer explanation?

If something fails, the steps and error code are useful. There is no need to post the ebook itself.