Revival of the JTidy Project updated to work with HTML5 new tags. Along with new option to not remove unknown tags:

Tidy tidy = new Tidy();
tidy.setDropProprietaryTags(false);

JTidy is a Java port of HTML Tidy, a HTML syntax checker and pretty printer. Like its non-Java cousin, JTidy can be used as a tool for cleaning up malformed and faulty HTML. In addition, JTidy provides a DOM interface to the document that is being processed, which effectively makes you able to use JTidy as a DOM parser for real-world HTML.

JTidy project on SourceForge.net seemed to fall into disrepair years ago and had not been updated for years. A few had forked it on Github. William L. Thomson Jr. came along and created a fork of others forks with a tag for his packaging needs as a dependency for JMeter. Then another came along, Dell Green who noticed some issues, tests failing, and undertook fixing both.

Since the code belonged to neither, William decided to create a JTidy organization and revive the project via community support. Which you are welcome to join in. Eventually this should become the official new home for JTidy.

Thanks to all past authors and developers. Those of which who could be found on Github have been invited to join this project. Along with those that this repository was forked from.