Windows. Based on an SGML parser. Shareware.

Windows. HTML, XHTML, and CSS validator. Also checks accessibility, links, and spelling. Commercial pro version and free lite version.

Perl script which corrects incompatible HTML generated by Microsoft applications.

Windows. Optimizes HTML documents removing unnecessary HTML code while checking links. Commercial software with free trial.

Windows. Includes validator, image scanner, meta tag manager, find and replace tool, tag pair fixer, and an HTML to text converter. Commercial software; 30-day demo.

Windows. Removes unnecessary characters from HTML, CSS, Perl, JavaScript and many other web file formats. Commercial pro version and free light version.

Unix, Windows, MacOS, and others. Validator fixes errors in HTML and XHTML. Converts HTML to XHTML. Free Software.

Unix and Windows. Lint and link checker. Commercial software; free trial. Also online checking.

Windows and Unix. Object-oriented toolkit for SGML parsing and entity management. Can validate any version of HTML for which a DTD is available. Free Software.

Windows. Instructions for the Do-it-yourself Offline HTML Validator using SP.

Unix. Generates statistics and finds inconistencies in a subweb (web site).

MacOS. Image and HTML lint. Commercial software; partially-functional demo.