29 June 2016.
This release includes a change to make <!--> (IE conditional comment end) a non-error again, as well as a change to ensure that in output from the JSON/gnu message formats, each message emitted always includes the URL/filename of the document being checked, along with a change to cause <template> contents to be hidden from outline views.
The list of substantive changes otherwise remains the same as in the 16.6.18 release, which makes <link rel=stylesheet> within the body a non-error, as well as also making the link rel values dns-prefetch, preconnect, prefetch, preload, and prerender non-errors (including in the body), and making a[rel=noopener] and area[rel=noopener] non-errors. In addition: <style scoped> and <iframe seamless> are now errors (because they’ve been dropped from the HTML spec), using multiple <meta charset> elements is now an error, allow-presentation & allow-orientation-lock are now allowed values for iframe[sandbox], and complete checking for the (complicated) microsyntax of the autocomplete attribute is now performed. Finally, comment checking has been experimentally changed in this release (to match a recent change to the HTML spec) such that the checker no longer emits errors for "--" (consecutive hyphens) in a comment but does now emit specific error messages for "<!--" (nested comment) within a comment, and "--!>" at the end of a comment (should be just "-->").
More: https://github.com/validator/validator/blob/master/CHANGELOG.md#16629
The files in this release provide a portable standalone version of the Nu Html Checker in two different forms: as a Java jar file, and as a Java war file.
Use the jar file either for batch checking of documents from the command line and other scripts/apps, as documented at https://validator.github.io/validator/, or as a self-contained service for browser-based checking of HTML documents over the Web—similar to https://checker.html5.org/ and https://html5.validator.nu/ and https://validator.w3.org/nu/.
Use the war file to deploy the Nu Html Checker through a servlet container such as Tomcat, as documented at https://validator.github.io/validator/#servlet.