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Compress EPUB
Shrink EPUB files by re-encoding images and stripping bloat — entirely in your browser. Free, no upload, no limits.
01Select your EPUB
How to compress an EPUB
Select your EPUB file
Open the file from your device. It is read by your browser directly — nothing is uploaded anywhere.
Pick a compression preset
Choose lossless cleanup, an e-reader tuned preset, or a target file size in MB. We estimate the result for each before you commit.
Download the smaller EPUB
The compressed book is saved straight back to your device. Your original file is never modified.
Frequently asked questions
Is compressing an EPUB safe for my book?
Yes. Text, chapters, and metadata are copied through byte-for-byte — only images are re-encoded, and the cover gets gentler treatment than the rest. The output is a standard EPUB that opens in any reader.
Will the images look worse after compression?
It depends on the preset. Balanced and E-reader keep quality high enough that most readers never notice. If you want zero changes to images, use the Lossless preset — it only strips junk files and repacks the archive.
Why did my file barely shrink?
EPUB size is mostly images. If your book is mostly text, or its images are already well optimized, there is little to reclaim — the tool tells you this upfront based on its analysis. A zip bomb of already-compressed media cannot shrink further.
Does my file get uploaded to a server?
No. Every step — reading the EPUB, re-encoding images, repacking the zip — runs in your browser on your device. You can disconnect from the internet after the page loads and the tool keeps working.
Will the compressed EPUB still open on my Kindle or Kobo?
Yes. The output keeps the same EPUB structure (including the required mimetype entry) as the original, so any device or app that opened the original will open the compressed version.