Online Markup Validator

This tool analyzes user-provided markup content to check conformance with HTML5 and XML well-formedness rules. It parses the input, builds a structural model, and reports syntax errors, misplaced tags, and attribute issues. It does not render the page but focuses on correctness, enabling developers to catch problems early. Users input a snippet or fragment; the service selects the appropriate parser (HTML5 or XML) and returns a structured list of errors with line and column positions, a severity level, and suggested fixes. The validator emphasizes actionable diagnostics over vague messages, so engineers can pinpoint the exact location and nature of each problem. Benefits include faster debugging, higher code quality, and reduced risk of runtime rendering glitches. Core value lies in early quality assurance for markup across teams, including frontend developers, content editors, and QA specialists. Core features include single-field input, mode selection, precise error reporting, and an exportable diagnostic payload for integration with CI pipelines. Use cases span validating snippets during content creation, checking CMS templates, and auditing legacy markup for modernization.