CINXE.COM
About the W3C Markup Validation Service
<!doctype html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=utf-8"> <title>About the W3C Markup Validation Service</title> <link rel="help" href="mailto:www-validator@w3.org"> <link rel="shortcut icon" href="images/favicon.ico" type="image/x-icon"> <link rel="start" href="./" title="Home Page"> <link rel="stylesheet" href="./style/base" type="text/css" media="all"> <meta name="keywords" content="HTML, HyperText Markup Language, Validation, W3C Markup Validation Service"> <meta name="description" content="W3C's easy-to-use markup validation service, based on SGML and XML parsers."> </head> <body> <div id="banner"> <h1 id="title"> <a href="https://www.w3.org/"> <img alt="W3C Logo" width="110" height="61" id="logo" src="./images/w3c.png" /> </a> <a href="./"><span>Markup Validation Service</span></a> </h1> <p id="tagline">Check the markup (HTML, XHTML, …) of Web documents</p> </div> <div class="doc"> <div><a id="skip" name="skip"></a> <h2>About The W3C Markup Validation Service</h2> <h3 id="TableOfContents">Table of contents</h3> <div id="toc"> <ol> <li><a href="#about">About this service</a></li> <li><a href="#others">Other resources</a></li> <li><a href="#credits">Credits</a></li> </ol> </div> <h3 id="about">About this service</h3> <p> The <a href="./">Markup Validator</a> is a free service by <abbr title="World Wide Web Consortium">W3C</abbr> that helps check the validity of Web documents. </p> <p> Most Web documents are written using <em>markup languages</em>, such as <abbr title="HyperText Markup Language">HTML</abbr> or <abbr title="eXtensible HyperText Markup Language">XHTML</abbr>. These languages are defined by <em>technical specifications</em>, which usually include a machine-readable <em>formal grammar</em> (and vocabulary). The act of checking a document against these constraints is called <a href="docs/help.html#validation_basics" title="Introducing and defining the concept of Markup Validation">validation</a>, and this is what the Markup Validator does. </p> <p> Validating Web documents is an important step which can dramatically help improving and ensuring their quality, and it can save a lot of time and money (read more on <a href="docs/why.html" title="Why validate? A document answering questions on the importance of validation." >why validating matters</a>). Validation is, however, neither a full <a href="docs/help.html#validandquality">quality check</a>, nor is it strictly equivalent to <a href="docs/help.html#validandconform" title="Read more about the difference between validation and conformance checking"><em>checking for conformance</em></a> to the specification. </p> <p> This validator can process documents written in most markup languages. Supported document types include the <abbr title="HyperText Markup Language">HTML</abbr> (through <abbr title="HyperText Markup Language">HTML</abbr> 4.01) and <abbr title="eXtensible HyperText Markup Language">XHTML</abbr> (1.0 and 1.1) family, MathML, SMIL and <abbr title="Scalable Vector Graphics">SVG</abbr> (1.0 and 1.1, including the mobile profiles). The Markup Validator can also validate Web documents written with an <a href="docs/sgml.html" title="introduction to the concepts of SGML and DTDs"><abbr title="Standard Generalized Markup Language">SGML</abbr> or <abbr title="eXtensible Markup Language">XML</abbr> <abbr title="Document Type Definition">DTD</abbr></a>, provided they use a proper document type declaration. </p> <p>This validator is also <q cite="https://www.cs.tcd.ie/15445/15445.HTML#SYSVALID">An HTML validating system conforming to International Standard ISO/IEC 15445—HyperText Markup Language, and International Standard ISO 8879—Standard Generalized Markup Language (SGML)</q> – which basically means that in addition to W3C recommendations, it can validate according to these ISO standards.</p> <p> Related resources include: </p> <ul> <li>The <a href="docs/">Documentation</a> for the Markup validation contains a lot of information on usage, installation, and development. Notably, the <a href="docs/help.html">Help and <abbr title="Frequently Asked Questions">FAQ</abbr></a> document contains a lot of information, and is a recommended reading.</li> <li>The <a title="Source Code for The W3C Markup Validation Service" href="source/">Source code availability</a> information page .</li> <li><a href="todo.html">The development roadmap</a> for this service.</li> <li><a href="feedback.html">How to provide feedback on The <abbr title="World Wide Web Consortium">W3C</abbr> Markup Validation Service</a>.</li> </ul> </div> <h3 id="others">Other resources</h3> <div> <h4>Documentation & Specifications</h4> <ul> <li><a href="http://www.w3.org/MarkUp/"><abbr title="World Wide Web Consortium">W3C</abbr>'s <abbr title="HyperText Markup Language">HTML</abbr> home page</a>.</li> <li><a href="http://www.w3.org/TR/html401/">The <abbr title="HyperText Markup Language">HTML</abbr> 4.01 specification</a>.</li> <li><a href="http://www.w3.org/TR/xhtml1/"><abbr title="eXtensible HyperText Markup Language">XHTML</abbr> 1.0: The Extensible HyperText Markup Language</a>.</li> <li><a href="http://www.w3.org/TR/xhtml11/"><abbr title="eXtensible HyperText Markup Language">XHTML</abbr> 1.1: Module-based <abbr title="eXtensible HyperText Markup Language">XHTML</abbr></a>.</li> </ul> </div> <div> <h4>Online Tools & Other Validators</h4> <p>In addition to this validator, the W3C is offering a number of other tools to help you check other types of documents (CSS, RDF, P3P, ...), find broken links in your Web pages, and so on. All these tools are listed on the W3C's <a href="http://www.w3.org/QA/Tools/"><abbr title="Quality Assurance">QA</abbr> Toolbox</a>.</p> <p>There are also many excellent tools developed outside W3C to help improve the quality of Web pages:</p> <ul> <li><a href="http://tidy.sourceforge.net/"><abbr title="HyperText Markup Language">HTML</abbr> tidy</a>, originally developed at W3C, is a program that can help automatically clean up HTML pages. </li> <li>The <a href="http://www.htmlhelp.com/tools/validator/"><abbr title="Web Design Group">WDG</abbr> <abbr title="HyperText Markup Language">HTML</abbr> validator</a> is another excellent online validation service.</li> <li><a href="http://arealvalidator.com/">A Real Validator</a> is a shareware <abbr title="HyperText Markup Language">HTML</abbr> syntax checker for Windows systems, from the author of the <abbr title="Web Design Group">WDG</abbr> validator.</li> <li><a href="http://valet.webthing.com/">Site Valet</a> by Nick Kew is a comprehensive set of Quality Assurance tools for checking and monitoring your web sites.</li> </ul> <p> The <abbr title="World Wide Web Consortium">W3C</abbr> also hosts a number of other <a href="http://www.w3.org/Status">Open Source software projects</a>. </p> </div> <h3 id="credits">Credits</h3> <p> The <a href="http://lists.w3.org/Archives/Public/www-html/1994Jul/0015">first online <abbr title="HyperText Markup Language">HTML</abbr> validation service</a> was created by <a href="http://www.w3.org/People/Connolly/">Dan Connolly</a> and <a href="http://www.markgaither.com/">Mark Gaither</a>. </p> <p> The <abbr title="World Wide Web Consortium">W3C</abbr> Markup Validation Service was created and maintained by <a title="Gerald Oskoboiny's Home Page" href="http://www.w3.org/People/Gerald/">Gerald Oskoboiny</a>. In a previous incarnation it was known as "The Kinder, Gentler, <abbr title="HyperText Markup Language">HTML</abbr> Validator" ("Kinder, Gentler" than Dan and Mark's original), but has since found a new home at <abbr title="the World Wide Web Consortium">W3C</abbr>, and is now maintained under the auspices of the <a href="http://www.w3.org/QA/">Quality Assurance</a> Activity. </p> <p> This service uses: </p> <ul> <li><a href="http://www.perl.org/">Perl</a> and many excellent open source Perl modules (see list in <a href="docs/install.html#install-prereq">installation documentation</a>)</li> <li> A derivative version of <a href="http://www.jclark.com/">James Clark</a>'s excellent <a href="http://www.jclark.com/sp/"><abbr title="Standard Generalized Markup Language">SGML</abbr> (and <abbr title="eXtensible Markup Language">XML</abbr>) parser</a> <abbr title="SGML Processor">SP</abbr>. The version in use for this service is the "OpenSP" version from the <a href="http://openjade.sourceforge.net/">OpenJade</a> team. For some time it also made use of <a href="http://www.htmlhelp.com/%7Eliam/">Liam Quinn</a>'s modified version, lq-nsgmls. </li> <li>Documentation and Error Explanations originally written by Scott Bigham.</li> <li>Interface and Design refinements by Valerio Proietti (and powered by <a href="http://mootools.net/">Mootools</a>)</li> <li> <p>Patches, Documentation and Ideas from: <a href="http://www.aaronsw.com/">Aaron Swartz</a>, <a href="http://bjoern.hoehrmann.de/">Björn Höhrmann</a>, Brett Bieber, Chris Lilley, Christian Smith, Christoph Päper, <a href="http://www.w3.org/People/Connolly/">Dan Connolly</a>, <a href="http://dorward.me.uk/">David Dorward</a>, <a href="http://www.tibbe-online.de/">David Tibbe</a>, Etienne Miret, Frank Ellermann, <a href="http://www.w3.org/People/Hugo/">Hugo Haas</a>, Henri Sivonen, Ian Hickson, <a href="http://www.jibbering.com/">Jim Ley</a>, <a href="http://www.cs.tut.fi/~jkorpela/">Jukka Korpela</a> <a href="http://www.w3.org/People/karl/">Karl Dubost</a>, <a href="http://www.htmlhelp.com/%7Eliam/">Liam Quinn</a>, <a href="http://www.w3.org/People/D%c3%bcrst/">Martin Dürst</a>, Moto Ishizawa, <a href="http://www.webthing.com/~nick/">Nick Kew</a>, <a href="http://www.w3.org/People/olivier/">Olivier Thereaux</a>, Patrick H. Lauke, Roland W. Crowl, Scott Bigham, <a href="http://sierkbornemann.de/">Sierk Bornemann</a>, <a href="http://www.webstandards.org/about/members/steph/">Steph Troeth</a>, <a href="http://inamidst.com/sbp/">Sean B. Palmer</a>, Shane McCarron, Terje Bless, Ville Skyttä, <a href="http://lists.w3.org/Archives/Public/www-validator/">...and the great user community on www-validator@w3.org.</a> </p> </li> </ul> </div> <ul class="navbar" id="menu"> <li><a href="/" accesskey="1" title="Go to the Home Page for The W3C Markup Validation Service">Home</a><span> | </span></li> <li><a href="/about.html" title="Information About this Service">About...</a><span> | </span></li> <li><a href="/whatsnew.html" title="The changes made to this service recently">News</a><span> | </span></li> <li><a href="/docs/" accesskey="3" title="Documentation for this Service">Docs</a><span> | </span></li> <li><a href="/docs/help.html" title="Help and answers to frequently asked questions">Help & <abbr title="Frequently Asked Questions">FAQ</abbr></a><span> | </span></li> <li><a href="/feedback.html" accesskey="4" title="How to provide feedback on this service">Feedback</a><span> | </span></li> <li><a href="/contribute.html" title="How to contribute to the validator project">Contribute</a><span> | </span></li> </ul> <div id="footer"> <p id="activity_logos"> <a href="https://www.w3.org/Status" title="W3C's Open Source, bringing you free Web quality tools and more"><img src="https://www.w3.org/assets/logos/w3c/w3c-no-bars.svg" alt="W3C" width="72" height="47"><img src="./images/opensource-55x48.png" alt="Open-Source" title="We are building certified Open Source/Free Software. - see www.opensource.org" width="55" height="48"></a> </p> <p id="support_logo"> <a href="https://www.w3.org/donate/"> <img src="https://www.w3.org/QA/Tools/I_heart_validator" alt="I heart Validator logo" title="Donate to W3C" width="80" height="15"> </a> </p> <p class="copyright"><span lang="en" dir="ltr">Copyright © 2024 <a href="https://www.w3.org/">World Wide Web Consortium</a>. <abbr title="World Wide Web Consortium">W3C</abbr><sup>®</sup> <a href="https://www.w3.org/policies/#disclaimers">liability</a>, <a href="https://www.w3.org/policies/#trademarks">trademark</a> and <a rel="license" href="https://www.w3.org/copyright/document-license/" title="W3C Document License">permissive license</a> rules apply.</span></p> </div><!-- footer --> <script src="https://www.w3.org/QA/Tools/w3c-include.js"></script> </body> </html>