ValidateHTML
ValidateHTML is a web tool designed to check HTML code and live URLs against modern HTML5 standards and web best practices. It detects unclosed tags, missing required attributes, deprecated elements, accessibility violations, and SEO-critical markup issues. Unlike traditional validators, it provides an instant quality score and letter grade based on severity filters to help developers track and improve code quality over time without requiring registration.
Checked on Sep 30, 2026.
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