Validation and Optimization Tools

Format On-line Validation
HTML / XHTML W3C HTML Validation Service
CSS W3C CSS Validation Service
Accessibility Cynthia Says Portal - Section 508 & WCAG
Accessibility Bobby
RSS RSS Feed Validator
HTML / XHTML CSE HTML Validator Lite On-line


  • W3C HTML Validation Service
    This is an easy-to-use HTML validation service based on an SGML parser. It checks HTML documents for compliance with W3C HTML Recommendations and other HTML standards.
    Originado do A Kinder, Gentler HTML Validator (HTML 3.2 Check).
  • W3C CSS Validation Service
    Validate your cascading style sheets.
  • Cynthia Says Portal
    Cynthia is a web content accessibility validation solution. Acessibility Reports based on U.S. Section 508 & WCAG 1.0 Priorities 1, 2, 3.
  • Bobby
    Bobby is a free service, created by Center for Applied Special Technology (CAST) and now provided by Watchfire, to help Web page authors identify and repair significant barriers to access by individuals with disabilities, as well as identify compatibility problems on HTML pages. Basta fornecer o URL da página e escolher o tipo de compatibilidade desejada e BOBBY examina a página e retorna um relatório completo. If you wish to test an entire site as a batch, there's a downloadable version of Bobby.
  • RSS Feed Validator
    This is a validator for syndicated feeds. It works with RSS 0.91, 0.92, 0.93, 0.94, 1.0, and 2.0. It also validates Atom feeds.
    The validator is open source, written in Python, and distributed under the same license as Python itself. To run it, you will need Python 2.2 or later, and an XML parser. Designed by Mark Pilgrim, wrote by himself and Sam Ruby.
    SourceForge Project: FeedValidator.
  • WDG HTML Validator
    Developed and maintained by Liam Quinn, The Web Design Group -
    The WDG HTML Validator is similar in many ways to the W3C HTML Validation Service and the (now unavailable) WebTechs Validation Service.
    WDG HTML Validator was released as open source, to facilitate further development. The source is released under Perl's Artistic License, which means that you may modify and distribute the source with few restrictions.
  • WDG CSSCheck
    Enter the URL of a Cascading Style Sheet, or enter your style sheet directly. Alternatively, you can use CSSCheckUp to check files uploaded from your computer.
  • Delorie Web Stuff
    Delorie Software provides interesting free services to assist web authors making their information available to the largest audience. These tools provide alternate ways of viewing your pages, so that you can ensure that your content is received properly by all viewers. Lynx Viewer, Search Engine Simulator, Web Page Purifier, Web Page Backward Compatibility Viewer, HTTP Header Viewer, HTTP Request Viewer.
  • NetMechanic
    Online Link Testing, HTML Validation
    Link Check, HTML Check, Browser Compatiblity, Load Time Check, Spell Check, GIFBot, Server Check, Server Check Pro.
    Server Check Free.
    NetMechanic Webmaster Tips Newsletter.
  • HTML Validator Pro
    Formerly Doctor HTML. Web page analysis tool for use over the World Wide Web or across company intra-nets behind a firewall. The program is written in Perl for easy adaptation to specific tasks. By Imagiware.
  • Perl CPAN: Weblint++
    Weblint is a syntax and minimal style checker for HTML: a Perl script which picks fluff off html pages, much in the same way traditional lint picks fluff off C programs. By Neil Bowers. Weblint is no longer being maintained. The latest stable version of weblint was released on September 1997.
    Weblint Gateways - Web-based interfaces which let you type in a URL and have it checked by weblint without having to install weblint locally:
  • Validation Bookmarklets
    By David Lindquist, an independent web developer.

Offline - Software

  • CSE HTML Validator
    The Professional HTML Syntax Checker, by AI Internet Solutions.
    CSE HTML Validator Professional is a award-winning commercial product. A time-limited demo is available for download.
    CSE HTML Validator Lite (FREE!).
  • A Real Validator
    Shareware HTML validator for Windows; offline version of the WDG HTML Validator. By Liam Quinn, The Web Design Group (WDG) -
  • HTML Tidy Project
    Dave Raggett's HTML TIDY (© W3C) is a free stand-alone utility for checking and pretty-printing HTML, that is in many cases able to automatically fix up mark-up errors and source editing mistakes, and tidy up sloppy editing into nicely layed out markup.
    HTML Tidy is available as W3C open source software, and also offers a means to convert existing HTML content into well-formed XML, for delivery as XHTML.
    HTML-Kit: A HTML Tidy graphical user interface for Windows 95/98/NT, by
  • HTMLTrim
    A highly customizable HTML/XHTML/XML pretty-printer and fixer for Windows. HTMLTrim is Open Source and distributed under a MIT license.
  • Xenu's Link Sleuth
    Xenu's Link Sleuth (Xenu) checks Web sites for broken links. Freeware for Windows. By Tilman Hausherr. Link verification is done on "normal" links, images, frames, plug-ins, backgrounds, local image maps, style sheets, scripts and java applets. It displays a continuously updated list of URLs which you can sort by different criteria. A report can be produced at any time.
  • AM-DeadLink
    AM-DeadLink detects dead links and duplicates in browser bookmarks/favorites (Internet Explorer, Firefox, Opera, Chrome), HTML files and URLs text files (tab/comma delimited). If a bookmark has become unavailable you can verify and delete it permanently. Additionally you can download FavIcons for all your Favorites and Bookmarks. AM-DeadLink is Freeware.
  • Webbot - the W3C Libwww Robot
    The webbot is a very fast Web walker with support for regular expressions, SQL logging facilities, and many other features. The webbot comes with the libwww codebase. It can be used to check links, find bad HTML, map out a web site, download images, etc.
    Libwww - the W3C Protocol Library: Source Distribution & Building / Installation.
    Precompiled libwww for Win32, by Vladimir A. Kozlov.
  • htmlchek
    By H. Churchyard, freely redistributable. Uma série de utilitários de validação e processamento de arquivos HTML. htmlchek version 4.1, Fevereiro 20 1995: valida HTML 2.0 e 3.0.