Compress E-Book
Reduce your EPUB file size right in the browser — re-encode cover art and illustrations, drop unused files and repack with maximum compression, all while keeping your book fully readable.
Why Compress with AnyDocFlow
Smart Image Compression
Cover art and embedded illustrations are decoded, downscaled to a sensible resolution and re-encoded — JPEG stays JPEG and PNG stays PNG, so the output always remains valid.
Unused-File Cleanup
The engine walks the OPF manifest and every link inside the book, then safely removes files nothing references anymore — stray thumbnails and leftovers that bloat the archive.
Maximum DEFLATE Repack
Everything that survives is repacked with the strongest DEFLATE compression, while mimetype stays the first, stored entry the EPUB specification requires.
Text & Layout Preserved
Only media files are touched. Your text, styles, table of contents and the package manifest pass through byte-for-byte, so the book reads exactly as before.
100% Local & Private
Compression runs entirely in your browser with a pure-JavaScript engine. Your e-book is never uploaded, so nothing leaves your device.
Three Compression Presets
Pick High quality, Balanced or Maximum size reduction for one file — switching a level re-compresses instantly so you can compare results.
About This E-book Compressor
EPUB files are ZIP archives, and most of their size comes from the images they embed — cover art, chapter illustrations and inline pictures. This tool attacks that size in three safe ways. First it re-encodes every embedded JPEG and PNG: images are downscaled to a sensible resolution and re-compressed, so visual quality stays high while the bytes shrink. Second, it finds files nothing in the book references anymore and removes them. Third, it repacks the whole archive with maximum DEFLATE compression, which alone often shaves 10–20% off text-heavy books. The only things that change are the image bytes and the archive structure — your text, styles, layout and table of contents survive untouched, and the output is a valid EPUB that keeps working on every reader. The entire job runs in your browser, so your files never leave your device.
How to Compress an E-book
Three quick steps — no sign-up, no upload, no cost.
Upload your e-books
Drag and drop one or more .epub files onto the upload area, or click to browse. Each package is read and its file size is shown next to it.
Choose a level and compress
Pick High quality, Balanced or Maximum size reduction, then click Compress. Every file is processed in turn and reports exactly how much smaller it got.
Download the results
Download files individually or grab them all in a single ZIP. Every output keeps its name with _compressed appended and stays a fully valid EPUB.
Important Notes
DRM-protected (encrypted) EPUBs cannot be compressed because their content is encrypted — the tool reports them as unreadable. Images below a small threshold are left untouched to avoid pointless quality loss, and any image that cannot be decoded is preserved byte-for-byte rather than risking a broken file. If re-packing does not actually make a file smaller, the original bytes are kept and you are told no reduction was needed. Compression only touches media files — text, styles, the manifest and navigation are preserved exactly. All processing happens on your device.