Tidy reads HTML, XHTML, and XML files and writes cleaned-up markup. For HTML
variants, it detects, reports, and corrects many common coding errors and
strives to produce visually equivalent markup that is both conformant to the
HTML specifications and that works in most browsers.

A common use of Tidy is to convert plain HTML to XHTML. For generic XML files,
Tidy is limited to correcting basic well-formedness errors and pretty printing.

If no input file is specified, Tidy reads the standard input. If no output file
is specified, Tidy writes the tidied markup to the standard output. If no error
file is specified, Tidy writes messages to the standard error.
For command line options that expect a numerical argument, a default is assumed
if no meaningful value can be found.

Tidy was written by Dave Raggett <dsr@w3.org>, and subsequently maintained by a
team at <http://tidy.sourceforge.net/>, and now maintained by HTACG
(<http://www.htacg.org>).