Open EPUB File

Information, tips and instructions

Validating an EPUB File

The International Digital Publishing Forum (better known by its acronym IDPF) has set the standard that EPUB files must meet. So that creators of eBooks in this format can be sure that their files comply with this standard, there is a validation process. Many files that fail IDPF validation do not look bad on e-readers, but will not be accepted by sales platforms. Others may be valid, but have editing errors. It can also happen that they are valid and well edited, but fail to provide any additional requirements of the sales platforms and, therefore, are rejected. Therefore, it is necessary to carry out the revision in this way: Check the ePub for errors first. Use the IDPF online tool (for files smaller than 10MB) or download the EpubCheck program. Once you are sure that you have a valid EPUB, we will review it on our own to ensure that everything is in order.

Important warning: Do not read your EPUB in Calibre before doing the validation, since when an EPUB is opened in the book viewer, the program creates a calibre_bookmarks.txt file inside the EPUB that generates rejection by some platforms.

Option 1: After creating your EPUB, add the original document again, either Word or edited in another program, preferably with another title, to avoid confusion, repeat the conversion process, reserve that EPUB for the Calibre viewer and leave the other intact.

Option 2 (recommended): If you do not have it on your computer, download Adobe Digital Editions for free, which will allow you to review your EPUB without generating any type of error. Once the program is installed, go back to Calibre and select the title of your book. After clicking Path: Click to Open (on the right), you will see your EPUB file inside the Calibre library folders. Open it with Adobe Digital Editions.

File Extension Info

EPUB Quick Info
  Electronic Publication
  application/xhtml+xml   application/epub+zip
Opens with
  Microsoft Edge
  Apple Books