In general, images included in an EPUB file should not exceed 4 million pixels.

For the cover image, the requirements are stricter: the size must not exceed 4 million pixels, and its smallest dimension (usually the width) must measure at least 600 pixels.


Good to know

When inserting a full-screen image into an EPUB file, whether the cover or another image, we recommend a width of 724 pixels for optimal display on the widest range of reading devices. This size will prevent the image from being cut in half because it is too large.