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PDF to EPUB Converter / Compress EPUB

Compress EPUB

Drop an EPUB, choose image quality and size, and download a smaller file. Only images (and fonts, if you choose) are touched; every other part of the book stays byte for byte the same.

Where an EPUB’s size comes from

  1. Choose the EPUB. DRM-protected books are refused.
  2. Set the quality and the largest image size. The default suits e-ink screens; raise it for colour tablets.
  3. Decide about fonts. Embedded fonts can be removed; the reader then uses its own.
  4. Compress and compare. The page shows before and after sizes. Download the result.

An EPUB is a zip of text files and images. The text is small and already compressed. Almost all of the weight is in images: photos stored at camera size, PNG files that hold photographs, and cover pages at several times the screen resolution. Embedded fonts add tens to hundreds of kilobytes each.

What each setting does

  • Image quality. JPEG quality used when a picture is saved again. 70 is a good e-ink value; below 50 shows blocks.
  • Largest image size. Pictures longer than this are scaled down. A 6-inch e-reader screen is about 1448 pixels tall, so 1600 is plenty there.
  • PNG photos to JPEG. A PNG that holds a photograph, without transparency, becomes a JPEG. Line art and images with transparency stay PNG. The book’s file list and every reference to the picture are updated.
  • Remove embedded fonts. Deletes the font files and their @font-face rules.

What is left alone

Text, styles, the table of contents, metadata and any image that would not get smaller are not touched. Their data is copied into the new file as it was. The book keeps its identifier, so your reader still treats it as the same book. If an EPUB is already tight, the page says so and you should keep the original. DRM-protected books are refused.

Questions people ask

How do I make an EPUB smaller?
Recompress its images. Most EPUB size is pictures, so lowering JPEG quality and limiting image size cuts the file a lot without changing the text. This page does that and shows the before and after size.
Does compressing hurt quality?
Slightly, for images only. At quality 70 and a 1600 pixel limit the difference is hard to see on a 6-inch screen. The text is never touched.
Will the compressed EPUB still open everywhere?
Yes. The output is a valid EPUB and was checked with the EPUB validator, with the same structure as the input.
Why is my result not smaller?
The book may have no large images, or its images may already be well compressed. Then the page tells you to keep the original.
Can I compress an EPUB with DRM?
No, DRM-protected books are refused.