This tool is an ongoing experiment in better HTML checking, and its behavior remains subject to change · Show sourceoutlineimage reporterrors & warnings onlycheck error pagesUser-Agent Accept-Language

Check for WCAG 2.0 parsing compliance: filters checker results to just show messages relevant to requirements in the WCAG 2.1 spec · Inswave have created the W3C Markup Validation Service for CSR pages, an extension for Chrome and Edge: ... To report bugs, request new features, or ask questions, please raise an issue or send mail to www-validator@w3.org. To run your own copy of the Nu Html Checker, get the latest release and read the following instructions on how you can use it both for:

This tool is an ongoing experiment in better HTML checking, and its behavior remains subject to change · About this checker • Report an issue • Version: 22.3.8

Please check it out before use the extension. HTML Validator (Chrome) Extension is a handy developer tool to provide HTML validation for your web page. It crawls your web page and send to W3C's web server for validation.

HTML Validator for Chrome is a browser extension that adds HTML validation inside Developer Tools of Chrome. The number of errors of a HTML page is seen with an icon in the browser status bar.

December 5, 2025 - It works on its server, so need to install it on the local machine. Powerful HTML validation feature as it uses Nu HTML Checker by the W3C.

Moved · See https://validator.github.io/validator/

Uses the Nu Validator. Cons: Can't be configured to use your own Validator instance. The overlay can be unusable when validating a page that already uses overlays. We also tried other extensions that are quite popular on the Chrome web store but, at the time of this writing, don't work: W3C Validator. Not an official W3C extension, it should use the legacy validator API and show the issues on the JS console, but it doesn't work. HTML Validator.

Grunt plugin for HTML validation, using the official Nu Html Checker (v.Nu) There was an error while loading. Please reload this page. validator/grunt-html’s past year of commit activity · JavaScript 185 MIT 41 2 0 Updated · Dec 3, 2025 · htmlparser Public ·

By running the HTML documents through a checker, it’s easier to catch unintended mistakes which might have otherwise been missed. Adhering to the W3C’s standards has a lot to offer to both the developers and the web users: It provides better browser compatibility, helps to avoid potential problems with accessibility/usability, and makes it easier for future maintenance. The Nu Html Checker(v.Nu) serves as the backend of html5.validator.nu, and validator.w3.org/nu.

The Nu Html Checker (vnu) — along with being usable as a standalone command-line client — can be run as an HTTP service, similar to validator.w3.org/nu, for browser-based checking of HTML documents, CSS stylesheets, and SVG images over the Web.

HTML Validator is a browser extension that adds HTML validation inside Firefox and Chrome. The number of errors of a HTML page is seen on the form of an icon in the status bar when browsing. The details of the errors are seen when looking the HTML source of the page.

The Nu Html Checker (vnu) — along with being usable as a standalone command-line client — can be run as an HTTP service, similar to validator.w3.org/nu, for browser-based checking of HTML documents, CSS stylesheets, and SVG images over the Web.

Maven plugin to validate HTML / CSS / SVG files with the NU HTML Checker (v.NU, https://validator.github.io/validator/) ... aar android apache api arm assets build build-system bundle client clojure cloud config cran data database eclipse example extension framework github gradle groovy io ios javascript jvm kotlin library logging maven mobile module npm osgi persistence plugin resources rlang sdk server service spring sql starter testing tools ui web webapp

This tool is an ongoing experiment in better HTML checking, and its behavior remains subject to change · About this checker • Report an issue • Version: 22.3.8

var checker = require('nu-html-checker'); var batch = checker.validate([ 'test.html', 'http://google.com' ]); batch.on('progress', function (e) { console.log(checker.format('stylish', e.value), '\n'); }); batch.on('end', function (err) { if (err) console.error(err.stack); }) When list is an array of strings, they can be either URLs or file paths.