As reported by eBook Newser in their post “IDPF Now Hosting an Epub3 Validator,” an ePUB 3.0 Validator is now available to run online (it also will handle ePUB2). The previous validator had been hosted on the Threepress Consulting Website, but with the acquisition of Threepress Consulting by O’Reilly’s Safari Books Online.
The new ePUB3 Validator based on EpubCheck and is hosted online by the IDPF here. It can only validate ePUBs that are 10MB or less. You just use the browse button to find the ePUB file you want to validate and then click the Validate button. The site will then tell you if your file validates; it if does not the validator will give you a list of errors in your ePUB.
If you have ePUB files over 10MB (often because they include a lot of images or multi-media content) or you need to validate many ePUBs at once, you will want to download EpubCheck and run it locally. EpubCheck 3.0 is available for download here. The current version is the fourth beta, and is now recommended for both EPUB 2.0(1) and 3.0 validation. Instructions for running EpubCheck from the command line are here.
Have you started creating ePUB3 files yet? Have you used the validator? Do you have any additional tips for running it?