Validating your book's technical accuracy is as important as proofreading for grammatical and spelling errors. It will ensure your book looks good and performs well.
Validation in the iBooks Store is based on EpubCheck. All EPUB deliveries to the iBooks Store undergo the validation process. If your EPUB doesn't pass validation, you will receive errors at the end of the delivery process. You can access an online version of EpubCheck at http://validator.idpf.org.
If you see error messages, follow these links:
- 
	
- Unmanifested file found or referenced resource missing errors 
	
- Attribute errors 
	
- Text not allowed error 
	
- Element errors 

Learn more about EpubCheck:
- 
	
- What’s a namespace? 
	
- Add alt text to images in an EPUB