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Compress EPUB

Reduce ebook file size by optimizing embedded images and repacking the archive.

or drop files here

Maximum file size: 200MB per file

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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.For an attachment, check the recipient’s stated limit and compare the downloaded file in bytes. MB and MiB differ: 1 MB = 1,000,000 bytes; 1 MiB = 1,048,576 bytes. A selected target is a request, not a guarantee.

How to Compress an EPUB File Online

1

Upload your EPUB files

Choose one or more `.epub` ebooks from your device.

2

Select image quality

Pick the quality profile for embedded covers and illustrations — text always stays untouched.

3

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.

EPUB - Wikipedia

The reflowable e-book packaging format built on open web standards.

W3C - EPUB 3 Specification

The W3C recommendation defining EPUB 3.

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