HTML5 Validator
Validate HTML5 markup for unclosed tags, structural issues, and malformed attributes with optional prettified output and Markdown reports.
How It Works
Paste or Upload HTML
Drop raw HTML from templates, CMS exports, or landing pages into the editor. The validator accepts full documents or snippets.
Configure Validation Output
Choose whether to show warnings and prettify valid markup. Adjust indentation to match your team’s coding standards.
Run Instant Analysis
The tool scans the DOM structure for unclosed tags, mismatches, and invalid attributes. Results are summarised with precise line numbers.
Review & Share Reports
Copy the Markdown report, download results, or share prettified markup with your team for quick fixes and QA documentation.
Problems It Solves
Problem
Broken HTML slips into production because structural issues are hard to spot in large files.
Solution
Automated validation pinpoints unclosed tags, invalid attributes, and mismatches with line numbers before deploys.
Problem
Marketing teams need readable reports when reviewing third-party HTML snippets.
Solution
Readable Markdown summaries and prettified output make stakeholder reviews painless.
Problem
Developers waste time manually reformatting HTML to understand validation errors.
Solution
Prettify and validate in one step, aligning code style and making diffs easy to understand.
Why Choose This Tool
Client-Side Validation
Run checks locally without sending markup to third parties — perfect for NDAs, unreleased campaigns, and internal dashboards.
Actionable Error Reports
Line numbers, instance paths, and human-readable messages keep designers and developers aligned on fixes.
Integrated Prettier
Optional prettify output leverages the HTML beautifier, so you can deliver clean markup alongside validation feedback.
History Friendly
Store runs with configuration snapshots to track QA cycles or document fixes for regulated industries.
Frequently Asked Questions
Does this validator support HTML5?
Will this tool prettify my HTML?
Do you send my HTML to a server?
Can I ignore warnings?
Does it detect accessibility issues?
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