Kindle EPUB Fixer

Why “no upload” matters

Every conventional converter site works the same way: your file travels to their server, sits in their queue, gets converted on their hardware, and – you hope – gets deleted afterwards. You can’t verify any of it. The FBI has even warned about free converter sites that use that upload as a way to deliver malware or harvest the documents themselves. The book you’re fixing may be your own manuscript; it deserves better than a stranger’s server.

ebook.tools removes the question entirely. The converter is delivered to your browser as code and runs on your machine; the file you drop is opened from memory, transformed, and saved back – the network isn’t involved at all. That isn’t a policy promise, it’s an architecture, and you can test it: load this page, switch off your wifi, and convert. It works exactly the same, because there was never anything to send.

Why Send to Kindle rejects EPUBs, and what the fixer does

Since Amazon retired MOBI uploads, Send to Kindle accepts EPUB – but it enforces limits that trip up perfectly good books. The hard one is size: anything over 200MB is refused outright. Then come the quieter rejections: a malformed package file, missing language metadata, broken internal references, or text encodings Kindle's importer refuses to guess at. Amazon's error messages rarely say which of these hit you. The result is the classic "epub won't send to kindle" afternoon.

This tool leads with diagnosis, not blind conversion. Drop your EPUB and you get a report: total size, how much of it is images, which images are oversized, and any structural or metadata problems we can detect. Only then do you choose to fix.

The fix pass does four things. It recompresses oversized images – the cause of almost every 200MB rejection – capping them at Kindle's usable resolution (there is no visible difference on an e-ink screen, where a 4000-pixel-wide photograph is pure wasted bandwidth). It strips junk files left behind by other apps (iTunes artifacts, thumbnail caches). It repairs the metadata Kindle actually checks, like a missing language declaration. And it repackages everything correctly, with the container structure the spec requires.

What it never touches: your text. Not one word, not one comma. The fixer treats book content as read-only and confines itself to images, packaging and metadata – so the fixed file is your book, just lighter and better-formed. Because it all runs in your browser, your possibly-unpublished manuscript stays yours alone.