Epub Compressor
Shrink an Epub by recompressing its images and, if you want, removing embedded fonts. Your text is never touched. Everything runs in your browser.
What actually makes an Epub big
Almost always the images. Export tools routinely pack print-resolution photographs into ebooks that display them at a fraction of the size, and a handful of 3 MB images turns a novel into a 40 MB file. The second offender is embedded fonts, which add hundreds of kilobytes each and which most readers override with the user's preferred font anyway.
What this tool does
It lists the images and fonts in your book with their sizes, then rebuilds the book with
the images re-encoded at the quality and resolution you choose. A replacement is only kept
when it is actually smaller than the original, so the tool never makes your book worse. Font
removal deletes the font files, their manifest entries and the @font-face rules
that reference them, which keeps the book valid; you can check the result with the
checker.
Why size matters on KDP
Amazon charges a delivery fee per megabyte on the 70% royalty plan, so an oversized book quietly taxes every single sale. Shrinking a bloated file before upload is one of the few one-click actions that directly increases your royalty. The same is true in reverse for readers: a smaller book syncs faster and fits more on an older device.