Validate HTML against W3C standards
SkillWeb & browsingw3c-compliant is a skill that lets an AI agent validate HTML against W3C standards. It is used when reviewing templates, rendered HTML, or shared components, and it checks the final browser-facing markup rather than just the source framework abstraction.
Use Validate HTML against W3C standards in Claude, ChatGPT or Ahel Desktop
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Then ask your AI: use the Validate HTML against W3C standards skill
Details
Instructions available. Your AI can read the instructions. Execution depends on the setup they require.
Account requirements not reviewed. Check the skill instructions before use; ahel provides instructions and does not run this skill.
No other account needed.
Have an AI agent that can load skills.
What your AI can do with it
- Validate HTML against official W3C standards
- Review templates for standards compliance
- Check rendered HTML, not just source framework abstraction
- Validate shared components before they are reused
- Review final browser-facing markup before shipping
Getting started
- Have an AI agent that can load skills.
- Add the w3c-compliant skill to the agent's available skills.
- Ask the agent to review a template, rendered HTML page, or shared component, and it will validate the markup against W3C standards.
What this skill tells your AI
The instructions your AI receives, as published by thedaviddias/front-end-checklist in skills/w3c-compliant/SKILL.md and read by ahel’s review.
Invalid HTML causes unpredictable rendering across browsers, breaks accessibility tools, and makes debugging significantly harder.
Quick Reference
- Use validator.w3.org or browser extensions for validation
- Fix errors first, then warnings (errors cause rendering issues)
- Integrate validation into CI/CD with html-validate
- Common issues: unclosed tags, invalid nesting, missing attributes
Check
Validate HTML markup using the W3C HTML Validator to identify and fix markup errors that could cause cross-browser compatibility issues.
Fix
Run HTML through W3C validator and fix reported errors including unclosed tags, missing attributes, and invalid nesting.
Explain
Explain why W3C HTML validation is important for cross-browser compatibility, accessibility, and maintainable code.
Code Review
Review templates, server-rendered HTML, and shared components that output markup related to Validate HTML against W3C standards. Flag exact elements, attributes, and routes where the rendered HTML violates the rule.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/html/w3c-compliant
Signals
- GitHub stars
- 74k
- Forks
- 7k
- Last commit
- Oct 2026
ahel review
K1binfo
installs-packages (in references/rule.md)
Automated review, not a security audit. Ruleset v1+k2.
Questions
- Does it check source code or the rendered output?
- It validates the final browser-facing markup, not just the source framework abstraction.
- When should the skill be used?
- Use it when reviewing templates, rendered HTML, or shared components that need to be validated against W3C standards.
- What standards does it validate against?
- It validates HTML against official W3C standards.
Advanced
- Item type
- skill
- Key
w3c-compliant- Source
- github.com/thedaviddias/front-end-checklist
github.com/thedaviddias/front-end-checklist
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