Compress EPUB
Make an EPUB smaller by recompressing the images inside it. Text, chapters and styling are not touched.
Target: 25.00 MB
What this page is for
An EPUB is a small website in a ZIP file. The text is tiny; cookbooks, comics, photo books and textbooks are large because of their images. This page recompresses those images and rebuilds the EPUB so it can be emailed or uploaded to a reader app.
It works on DRM-free EPUBs, such as ones you wrote, exported, or bought without copy protection.
The rule: size limits, and the one EPUB rule that must not break
Email limits apply as usual: 25 MB in Gmail (about 18 MB of real file after encoding) and 20 MB in Outlook.com. Reader apps and stores publish their own limits; check yours.
The EPUB format requires a file called mimetype to be first in the archive and stored uncompressed. Many quick zip tools break that and the reader refuses the book. This page keeps it first and uncompressed.
Worked example
60 MB cookbook with 300 full-size photos. Scaling photos to a longest side of 1280 px, which is still more than an e-reader screen shows, typically brings a book like that to between 10 and 20 MB.
How to use it
- Pick a target size.
- Tap Choose file and select the .epub.
- Tap Shrink the EPUB.
- Download the result and open it in your reader to check it.
Questions
Does it work on books from a store?
Only if they are DRM-free. With copy protection the images are encrypted, so there is nothing this page can read or shrink.
Will the text or formatting change?
No. Only JPEG and PNG images are re-encoded, and only when the new version is smaller.
Does it handle fixed-layout and comic EPUBs?
Yes. Images keep their names and aspect ratio, so page layouts that reference them are unaffected.
Is the book uploaded?
No. It is processed in your browser.
Related tools
Sizes and results are estimates produced by your own browser. A file that fits the cap is not a guarantee that the destination will accept it: services change their limits, and some check more than size. On iPhone and iPad, Safari limits memory and codecs, so large files can fail there that work on a computer. Keep your original file.