HTML Shrinker
- Windows. Removes unnecessary characters from HTML, CSS, Perl, JavaScript and many other web file formats. Commercial pro version and free light version.
- http://www.thepluginsite.com/products/htmlshrinker/

Firefox extension HTML Validator
- A W3C Tidy-based HTML Validator which checks pages from within the Firefox web browser.
- http://users.skynet.be/mgueury/mozilla/index.html

WebLight
- Linux, Mac OS X, and Windows. Finds broken links, non-standard HTML, and links between URIs on web sites. Commercial software; free for small sites.
- http://illumit.com/Products/weblight/

HTML Code Cleaner/Compressor
- Windows. Optimizes HTML documents removing unnecessary HTML code while checking links. Commercial software with free trial.
- http://www.htmlcodecleaner.com-http.com/

SWAN: SubWeb Analyzer
- Unix. Generates statistics and finds inconistencies in a subweb (web site).
- http://www.win.tue.nl/~wstomv/software/swan/swan.html

SP Instructions
- Windows. Instructions for the Do-it-yourself Offline HTML Validator using SP.
- http://ktmatu.com/info/do-it-yourself-offline-html-validator/

Demoroniser
- Perl script which corrects incompatible HTML generated by Microsoft applications.
- http://www.fourmilab.ch/webtools/demoroniser/

HTML PowerTools
- 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.
- http://tali.com/

SP
- 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.
- http://jclark.com/sp/

LinkScan/QuickCheck
- Unix and Windows. Lint and link checker. Commercial software; free trial. Also online checking.
- http://elsop.com/linkscan/

A Real Validator
- Windows. Based on an SGML parser. Shareware.
- http://arealvalidator.com/

HTML Tidy
- Unix, Windows, MacOS, and others. Validator fixes errors in HTML and XHTML. Converts HTML to XHTML. Free Software.
- http://www.w3.org/People/Raggett/tidy/

CSE HTML Validator
- Windows. HTML, XHTML, and CSS validator. Also checks accessibility, links, and spelling. Commercial pro version and free lite version.
- http://www.htmlvalidator.com/