Epubfix |best|

If you are a Python developer, you can automate this. Here is a mini-script that fixes 80% of common errors:

Repairs or adds missing language tags, titles, and author names required by retail platforms like Apple Books and Kobo. ePubFix

: A popular, lightweight web-based tool specifically designed to fix "weird symbols" (encoding issues) and bad formatting that often appear when using Amazon's Send to Kindle service. If you are a Python developer, you can automate this

: A commercial tool that includes an "EPUB-fix" feature. It is designed to repair damaged or "broken" EPUB files through a simple "Add > Fix" interface. Troubleshooting Guide: How to Fix a "Broken" EPUB : A commercial tool that includes an "EPUB-fix" feature

Calibre is free and incredibly effective. To use it for repair:

: It generates a "fixed" version of the EPUB (often adding a prefix to the filename for easy identification). : Use the official Amazon Send to Kindle page to upload the corrected file. Comparison: ePubFix vs. Calibre ePubFix (Online Tool) Calibre (Desktop App) Ease of Use : No installation required; works on mobile. : Requires software installation on a PC/Mac. Primary Use Quick fixes for "Send to Kindle" errors. Full library management and deep file editing. Local browser processing; no upload. Entirely offline on your local machine. Manual Control Automated common fixes.