HTML_CodeSniffer is a client-side script that checks HTML source code and detects violations of a defined coding standard.

HTML_CodeSniffer is written entirely in JavaScript, does not require any server-side processing and can be extended by developers to enforce custom coding standards by creating your own “sniffs”.

It can be used in two ways. Called directly in JavaScript source, HTML_CodeSniffer will provide a list of known and potential violations to the calling script. It also comes with a pop-up auditor interface, accessible via a bookmarklet, letting you browse through messages emitted from one of the defined standards. Where possible, the auditor also points you to the HTML element causing the problem.

HTML_CodeSniffer comes with a set of 3 standards that enforce the Web Content Accessibility Guidelines (WCAG) 2.0.