Fundraising for EPUBCheck

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This is a cross-post on behalf of the Publishing Working Group, a division of the W3C.

We Need Your Support: Join The Effort to Update The Tool We Use to Validate EPUB Files

Work to update epubcheck and make it useful in validating files begins in September 2018 … Will you contribute?

What is epubcheck?

A tool that validates EPUB files, epubcheck helps both content creators and content sellers/distributors to determine if a publisher’s or author’s digital book is ready to be released for distribution or sale. The tool can detect many types of errors in EPUB: container structure, packaging, metadata, content markup, and internal reference consistency are all checked to ensure that books work well and offer a reliable ereading experience. The whole ebook industry relies on epubcheck to guarantee the accuracy of ebooks, but epubcheck 4.0.2 has not been updated in a significant way since 2016. Without an upgrade, epubcheck will not be able to validate files created using newer versions of EPUB. In fact, in its current state, epubcheck cannot properly validate many EPUBs that meet the most up to date standards.

You already benefit from epubcheck

Most retailers will not accept an EPUB file unless it successfully passes epubcheck validation. During the creation process, files are typically run through epubcheck several times to ensure the accuracy of your product. Epubcheck is the decisive tool that allows developers and vendors to identify errors at an early stage and that keeps corrupt files out of circulation.

Now is the time to update epubcheck

The EPUB3 Community Group is updating the EPUB specification to address a set of issues that have prevented widespread adoption of EPUB 3.1. The new EPUB 3.2 specification that will be released in Fall 2018 is expected to help in several ways, but it needs a new epubcheck to accompany it.

Epubcheck plays a strategic role in the ebook production and distribution life cycle and as the EPUB specification evolves, so too does the need to update the tools we use to create and validate EPUB files. It needs a major upgrade for four primary reasons:

  1. To bring it in sync with the dynamically evolving core web specs of HTML, CSS, and SVG and also with the most current version of EPUB 3, which will be finished soon
  2. To fully support the EPUB Accessibility Guidelines, making your products usable for everyone
  3. To add new features, such as HTML validation (in coordination with the W3C validation services) and a better check of media overlays
  4. To offer better service to the publishing industry with a faster response to bug reports and feature requests

To ensure the availability of a reliable and up-to-date epubcheck tool, we ask for your financial contribution to this effort to overhaul the code and create a more stable toolset.

Now is the time to start work to validate files with these features, so that publishers and authors have confidence that the digital books they create will work in the broader marketplace.

Several sponsors have already committed funds to the epubcheck upgrade

Several sponsors have already committed funds to support for an update to epubcheck. Their foundational support is critical to the project, and we need to make sure that the resources are adequate to both update the tool and provide for its continued maintenance over the next two years.

Commitments to date total $46,000 and have been received from:

  • DAISY Consortium,
  • Google,
  • Macmillan Learning,
  • VitalSource.

We have selected DAISY’s proposal from a competitive selection process to update epubcheck. We anticipate a total sum of up to US$150,000 for the code work and maintenance that will be needed for this overhaul. Sponsors can join the effort for a contribution of $1,000 or more, with tiered support as follows:

  • Leadership Sponsors: US$20,000 or more
  • Sustaining Sponsors: US$15,000-19,999
  • Supporting Sponsors: US$10,000-14,999
  • Friend: US$5,000-9,999
  • Helper: US$1,000-$4,999
  • Or, whatever amount is good for you!

Your support for this development effort does more than demonstrate your commitment to digital publishing. It will deliver a tool that you, your company, and your customers will benefit from every day. A critical part of the digital book ecosystem, epubcheck delivers value by ensuring book files are ready to be distributed and consumed as intended. Readers love books that work.

You can contribute using the online contribution form that will help you registering your payment. Contributors can be acknowledged (via logo) on the epubcheck home page; the size of the logo will depend on the level of contribution.

This work is managed by the Steering Committee of the Publishing Business Group at W3C.

Organization Background

The World Wide Web Consortium (W3C) is an international community where Member organizations, a full-time staff, and the public work together to develop Web standards. Led by Web inventor and Director Tim Berners-Lee and CEO Jeff Jaffe, W3C’s mission is to lead the Web to its full potential. Contact W3C for more information.

Publishing@W3C is committed to continue to develop and promote EPUB 3 as the packaged accessible interchange and delivery format for digital publications. The EPUB 3 Community Group (“EPUB 3 CG”) provides a forum for ongoing technical development of EPUB 3 and related extension specifications and ancillary deliverables.

How can I get more information?

Contact Tzviya Siegman ( or Luc Audrain ( with questions or feedback.

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