Helicon Books validator

EPUB logo

The EPUB standard is a complicated standard that relies on other standards such as XML, HTML, CSS etc. 

Any mistake may lead to unreadable title, application crashes etc.

Major book distributors such as Apple, Kobo, Google etc. may have additional requirements in addition to validation.

Helicon Books validator performs a through validation for EPUB files according to the IDPF's EPUB standard, but it doesn't stop there. Tests are performed to make sure the book can be uploaded to various stores and warns about problems that may lead to issues when reading with various Reading Systems.

For more information about what is checked refer to our validation page.

Problems reported in short simple english text along with component name and line.



There are two kinds of problems: Errors and Warnings. Errors are problems that you must fix otherwise it will lead to undreadable title or application crashes. Warnings are less severe problems however it is still advised to fix them.

Pricing is in packages of credit. Each credit is one book, however in many cases when you are developing a new book, you have to test the same book several times, therefore there is a number of retests available for each book before it is considered a new book.

This product is currently in Beta therefore any new user registred automatically receives credit of 10 books with an option for 10 retests of book with same id.

For each book tested, the validator stores the bookid and modification time metadata it does not save the book itself or any other data.


Contact us at: info@heliconbooks.com for more information.

Frequently asked questions

Q. What files are tested?

A. Helicon Books validator tests only EPUB files, of versions 2, 3, 3.01 and also books created with EDUPUB profile.

Q. How much it cost?

A. See the prices page for prices. Currently the tool is in beta contact us to get 10 free book tests.

Q. Do you keep books that has been validated?

A. No Books are deleted as soon as validation is completed. We only record the book metadata such as: identifeir, name, file name, modification time etc.

Q. Do you use EPUBCHECK?

A. Yes, epubcheck version 4.0 is one phase of the validation

Q. What is tested?

A. Click here to read more about tests performed.

Q. What is the maximum file size that can be tested?

A. Maximal file size that can be uploaded to the server is 100M, contact us if you need larger files.