HTML Validator — On-Device

Validate the current page's HTML and accessibility markup, entirely on your device. No external validator to break.

🔍 VALIDATE HTML IN ONE CLICK Check the HTML and accessibility of any webpage directly in your browser. HTML Validator — On-Device uses a self-contained validation engine that runs locally. Your webpage content is never sent to an external validator, giving you fast, private, and reliable results—even when you are offline. ✅ WHAT IT CHECKS 🧩 HTML ERRORS Invalid or obsolete HTML elements and attributes Incorrect attribute values Misnested or unclosed elements Duplicate IDs Common HTML5 structural problems ♿ ACCESSIBILITY ISSUES Images missing alternative text Form controls without associated labels Missing language attributes Missing document titles Incorrect heading order 🛠️ BEST-PRACTICE ISSUES Unsafe links that open in a new tab Missing viewport configuration Common markup, usability, and development issues 🚀 KEY FEATURES ⚡ INSTANT VALIDATION Analyze webpages immediately without waiting for an external web service. 🎯 FIND ISSUES QUICKLY Click any reported issue to locate and highlight the affected element directly on the webpage. 🔢 LIVE ERROR BADGE View the number of detected errors directly on the extension toolbar. 🧹 CLEAR RESULTS Issues are organized by severity, including errors, warnings, and informational notices. Every issue is explained in simple language. 🔒 PRIVATE BY DESIGN Validation runs entirely inside your browser. Webpage content and visited URLs are never collected or transmitted. 🌐 WORKS OFFLINE The validation engine is built into the extension, so it continues working without an internet connection or third-party validator. 💪 BUILT FOR RELIABLE VALIDATION Many older validator extensions stopped working because they depended on external services. HTML Validator — On-Device includes its own modern HTML5 rules engine for dependable, long-term validation. 🛡️ PRIVACY All HTML and accessibility checks are performed locally on your device. The extension collects optional anonymous usage statistics, including feature usage counts, extension version, and general browser, operating system, and country information. This data helps us prioritize improvements. The extension never collects webpage content, visited URLs, or personal information. You can disable anonymous statistics at any time in Settings. Privacy Policy: https://crx-api.nexsage.com/policies/html-validator ✨ PLANNED PRO FEATURES Full-page WCAG 2.2 accessibility audits SEO and metadata validation JSON-LD structured-data checking Open Graph validation Exportable audit reports 🆕 WHAT’S NEW IN VERSION 0.2.0 Added optional anonymous usage statistics Added a first-run privacy notice Added a Settings toggle for disabling statistics HTML and accessibility validation remains completely on-device