Compress EPUB
Reduce ebook file size by optimizing embedded images and repacking the archive.
or drop files here
Maximum file size: 200MB per file
About EPUB Compression
EPUB files are ZIP archives whose size is dominated by embedded cover art and illustration images. This browser-based compressor re-encodes those images at your chosen quality and repackages the book — keeping the EPUB structure valid, including the required uncompressed mimetype entry. Your ebook never leaves your device, making it ideal for private libraries and self-published manuscripts.
How to Compress an EPUB File Online
Upload your EPUB files
Choose one or more `.epub` ebooks from your device.
Select image quality
Pick the quality profile for embedded covers and illustrations — text always stays untouched.
Compress and download
Process the books in your browser and download valid, smaller EPUB files when done.
Frequently Asked Questions
How does EPUB compression work?
EPUB files are ZIP archives containing XHTML text and images. Our tool re-encodes embedded images at optimized quality and repackages the archive, preserving the EPUB structure including the required uncompressed mimetype entry.
Will chapters and text change?
Chapters, text, navigation and metadata remain byte-for-byte identical. Only embedded images are re-encoded, so the reading experience is preserved.
How much can I reduce EPUB file size?
Image-heavy books like comics, cookbooks and textbooks can shrink by 50–80%. Text-only novels see modest gains from archive repacking.
Is this EPUB compressor free?
Yes, completely free with no limits. Process as many ebooks as you need, no registration required.
References & Resources
Authoritative specifications and references for the file formats this tool works with.
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