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BlueGriffon EPUB3 Validator

An add-on to Firefox to validate an EPUB3 package in just one click.

100% Java free, not based on EpubCheck

No command-line knowledge needed.

Install in 3 clicks, run in one click!


You can't make it simpler!

1. Select the menu item Tools > BlueGriffon EPUB3 Validator

2. Click to select a file or drag&drop it
file selection
3. Get the results!

What's inside

Our validator is written 100% in JavaScript and does not use the Java code of EpubCheck.

It includes it own content model validator for XML and its own CSS parser and validator for the EPUB3 Profile of CSS.


  1. Zip package integrity
  2. mimetype file as first file in package
  3. extra binary constraints on Zip package
  4. verification of mimetype
  5. existence and readability of directory
  6. verification of files allowed in META-INF
  7. existence and readability of container.xml file
  8. verification of all filenames in package according to file names and paths restrictions

OPF files

  1. existence and readability of file
  2. opf file extension
  3. XML content model
  4. version (3.0)
  5. parsing of the prefix attribute
  6. correctness of the unique-identifier attribute
  7. validity of dc:language and all xml:lang against BCP47
  8. validity of all meta properties including OPF meta element for compatibility reasons
  9. correctness of refines attributes
  10. verification of extra constraints not expressed in the schema
  11. presence of one and one only nav item element
  12. NCX presence (compatibility with EPUB2)
  13. validity of guide element and contained reference elements if present (compatibility with EPUB2)
  14. verification of all media types and presence of necessary fallbacks
  15. verification of item and itemref properties and type
  16. verification of all IDREFs
  17. verification of dates against ISO 8601
  18. existence and readability of targets of local link elements
  19. verification of handler elements


  1. existence and readability of file
  2. XML content model
  3. validity of all IDREFs
  4. validity of language codes against BCP47


  1. XML content model
  2. verification of media type of OPF files
  3. warning if more than one OPF declared (Reading Systems are not required to use any rendition except the default one)

Media Overlays

  1. existence and readability of file
  2. XML content model
  3. parsing of the prefix attribute
  4. validity of epub:type and epub:textref attributes

Content Documents

  1. existence and readability of file
  2. xhtml file extension
  3. parsable as xhtml5
  4. parsing of the prefix attribute
  5. validaty of epub:type and SSML attributes
  6. content model of epub:switch elements
  7. content model of epub:trigger elements
  8. validity of epub:trigger IDREF attributes
  9. extra constraints on Navigation Documents

CSS Profile

  1. existence and readability of file
  2. correctly dealing with nested imported stylesheets
  3. charset as UTF-8 or UTF-16 only
  4. verification of all style declarations, warning for properties outside of the profile
  5. validation of Media Queries
  6. exclusion of position: fixed
  7. exclusion of direction and unicode-bidi properties
  8. CSS 3 Speech properties with -epub- prefix
  9. CSS 3 Fonts font descriptors unprefixed
  10. CSS 3 Text properties with -epub- prefix
  11. CSS 3 Writing Modes properties with -epub- prefix
  12. CSS 3 Multi-column Layout properties unprefixed, including oeb-column-number alias
  13. e-pub-ruby-position property

More to come...

Contact us

You can contact us by email at or follow us on Twitter.

Buy it

Requires Firefox >= 12. Mac OS X, Windows, Linux.

License is for one single user on a single computer, please contact us for orders over ten units.

Buy it once, get free upgrades for life!

After purchase, you will receive an email containing a download link to the add-on.
Please save the add-on onto your hard disk and use Firefox's menu File > Open File to install the file.
Make then sure to double-check your email address in all purchase forms!

Add to Cart

To run the validator, use the Tools > BlueGriffon EPUB3 Validator menu item or
click on the add-on's icon in the Add-on toolbar (useful on Windows when the main menubar is collapsed).

Don't miss the context menu on the results' page...


Please file all bugs, suggestions and requests in our Bugzilla.

Product is "EPUB3 Validator add‑on to Firefox", component is "General"; please write in english.


1. Can I validate an EPUB2 package with your add-on?
No, we're focusing on EPUB3 only.
2. You said above "free upgrades for life". Really?
Yes, really. You'll receive by email all our future releases of this add-on. Bugfixes or new features. Minor or major. All.
3. You said above "More to come...". For instance?
  • validation of all CSS values
  • validation of html5 and SVG
  • presence of all replaced elements (images, videos, fonts, etc.)
  • etc.
4. When I try to pruchase your add-on, I end up on an "e-junkie" page..
Yes, e-junkie is a well-known shopping cart processor we use. It's extremely serious despite of their name. They think it's a cool name...
5. What kind of payment do you accept?
We use PayPal for all our payments. You can then use a PayPal account or any credit/debit card PayPal accepts.
6. Do you guys have special offers for site licenses or big numbers of licenses?
Yes we do. Please contact us.
7. What are the "Taxes" I see when I order the add-on?

It's VAT and it's only added to purchases made by european individuals and companies. That's absolutely mandatory, since we're also based in Europe. Nothing we can do about it, sorry.

It does not apply to customers outside of the European Union.

8. Who are you?

We're Disruptive Innovations SAS, a French software company founded in October 2003. Based in Saint-Germain en Laye, France, Disruptive Innovations SAS delivered in the past premium products like the popular editor Nvu to Linspire Inc. or the XML editor Etna to the Connexions Project.

We're also the authors of the BlueGriffon editor for the Web and the BlueGriffon EPUB Edition editor.

You can contact us at european business hours by phone at +33 1 3451 0722 or by email at