Content files meet the weight limit of the oldest playback systems
Although this is not an official EPUB requirement, it is recommended not to exceed 300 kilobytes for XHTML files. This limit is due to an older version of the Adobe Mobile Reader engine that could not manage larger files. If the XHTML file size was more than 300 kilobytes, the content beyond this limit was not displayed.
Objectives
Ensure that EPUB files are compatible with older playback systems, especially those with technical limitations.
Ensure maximum interference between different playback systems and platforms.
Enhance performance and upload time of EPUB files.
Implementation
XHTML files should be split in units with a maximum weight of 250 kB