HTML Validator

Validates HTML markup for syntax correctness and HTML5 conformance.
Accepts full documents or fragments and reports precise error locations to guide fixes.
Target users include web developers, editors, and QA engineers who need quick feedback during authoring, code reviews, or CI pipelines.
The validator helps ensure consistent rendering, accessibility indicators, and standards compliance before publishing.

Conceptually, the tool lexes and parses input HTML, then applies a rule set derived from the HTML5 specification to identify problems such as unclosed tags, mis-nested elements, invalid attributes, and mismatched quotes.
It normalizes input, detects encoding, and yields a structured errors list with line and column positions, an error code, and a suggested fix.
Errors are categorized as critical or warning to support triage in fast iteration cycles.

Unique value comes from fast, input-agnostic validation that works on snippets or full documents without rendering.
It integrates into development workflows, provides deterministic outputs suitable for automation, and exports reports for audits.
Core features include exact location data, a compact errors array, and optional batch validation for larger codebases.
This tool focuses on HTML markup quality, leaving CSS and JavaScript concerns to separate tooling.