HTML Validators

Total Validator – Downloadable Java-based desktop tool validates HTML / XHTML / WCAG / Section 508 / Links / Spelling; for Win/MAc/Linux. HTML validation against the W3C Specifications; accessibility validation against the WCAG (1.0 and 2.0) and US Section 508 standard; checks each page for broken links; spell checks (English, French, Italian, Spanish, German). 1-click validation if using the Firefox or Chrome extension. Free and pro versions.

Site Check – Free online tool from Jens Meiert; type in one URL and automatically run HTML and stylesheet validators,accessibility assessment, link check, load time check, and more. Organizes access to a collection of free online web test tools. Also lists a wide variety of free online web analysis/development/test tools.

Site Validator – Service that automatically validates HTML, CSS and Accessibility on any size site. Only need a starting URL; all site pages wilk be validated using W3C and Tenon and a summary and detailed report is produced. Can schedule for periodic automated validations. Can validate large sites and can submit an XML sitemap to specify a subset of pages to validate. Free standalone open source version also available as a Ruby gem.

RealValidator – Downloadable shareware HTML validator based on SGML parser by Liam Quinn. Unicode-enabled, supports documents in virtually any language; supports XHTML 1.0, HTML 4.01, HTML 4.0, HTML 3.2, HTML 3.0, and HTML 2.0 ; extensible – add proprietary HTML DTDs or change the existing ones; fetches external DTDs by HTTP and caches them for faster validation; For Windows.

HTML Validator – Firefox add-on, open source by Marc Gueury. The validation is done on your local machine inside Firefox and Mozilla. Error count of an HTML page is seen as an icon in the status bar when browsing. Can validate the HTML sent by the server or the HTML in the memory (after Ajax execution). Error details available when viewing the HTML source of the page. Based on Tidy and OpenSP (SGML Parser). Available in 17 languages and for Windows and other platforms.

CSE 3310 HTML Validator – HTML/XHTML/CSS syntax checker for Windows from AI Internet Solutions. Supports wide variety of standards; accessibility (508) checking; uppercase/lowercase converter, link checking, spell checking. Free ‘lite’ version. For Windows.

Web Page ‘Purifier’ – Free on-the-web HTML checker by DJ Delorie allows viewing a page ‘purified’ to HTML 2.0, HTML 3.2, HTML 4.0, or WebTV 1.1. standards.

W3C HTML Validation Service – HTML validation site run by the WWW Consortium (the folks who set web standards); handles one URL at a time; Can choose from among 30 character encoding types, and multiple HTML and XHTML document types/versions.

W3C CSS Validation Service – CSS validation site run by the WWW Consortium (the folks who set web standards); handles one URI at a time; or upload file or validate by direct input.

Web Page Backward Compatibility Viewer – On-the-web HTML checker by DJ Delorie; will serve a web page to you with various selectable tags switched on or off; very large selection of browser types; to check how various browsers or versions might see a page.

HTML TIDY – Free utility available from; originally by Dave Raggett. For automatic fixing of HTML errors, formatting disorganized editing, and finding problem HTML areas. Available as source code or binaries.