How do I check HTML accessibility?

Paste your HTML code into the accessibility checker, click Check Accessibility, and review the results. The tool checks for WCAG 2.1 AA compliance issues including missing alt text, improper heading hierarchy, missing ARIA labels, form label issues, and keyboard navigation problems. All checking happens locally in your browser for complete privacy.

What accessibility issues does the checker detect?

Our HTML accessibility checker detects WCAG 2.1 compliance issues including missing alt text on images (1.1.1), missing lang attribute (3.1.1), improper heading hierarchy (1.3.1), missing form labels (4.1.2), missing ARIA labels, keyboard navigation issues, and semantic HTML structure problems. It provides specific WCAG guideline references for each issue.

Does this checker test WCAG 2.1 compliance?

Yes. Our HTML accessibility checker tests for WCAG 2.1 Level A and AA compliance. It checks for missing alt text (1.1.1), language declaration (3.1.1), heading hierarchy (1.3.1), form labels (4.1.2), keyboard accessibility (2.1.1), and other WCAG 2.1 guidelines. Each issue includes the specific WCAG guideline reference.

What WCAG level does this checker test?

This accessibility checker tests for WCAG 2.1 Level A and AA compliance. Level A includes the most critical accessibility requirements (alt text, language, labels). Level AA includes additional requirements for better accessibility. The tool provides an accessibility score and compliance level based on WCAG 2.1 standards.

Free • Fast • Privacy-first

HTML Accessibility Checker

Q: Do you store my HTML code?

No. This HTML accessibility checker processes everything locally in your browser. Your code never leaves your device, ensuring complete privacy and security. No server uploads, no data storage, no privacy concerns.

Q: What's the difference between errors and warnings?

Errors are critical WCAG 2.1 Level A violations that must be fixed for accessibility compliance (missing alt text, missing lang attribute, missing form labels). Warnings are important but less critical issues (heading hierarchy skips, missing semantic elements). Suggestions are best practices for better accessibility beyond minimum requirements.

Test WCAG 2.1 AA compliance and ensure your HTML is accessible to everyone

Our free HTML accessibility checker helps you check HTML accessibility online for WCAG 2.1 AA compliance. This html accessibility checker no download tool ensures your website is usable by everyone, including users with disabilities. Check HTML for accessibility issues like missing alt text, improper heading hierarchy, missing ARIA labels, form label issues, and keyboard navigation problems. Validate HTML accessibility online instantly—all checking happens locally in your browser.

⚡ Check Accessibility How it works

WCAG Level: 2.1 AA
Standards: WCAG 2.1
Mode: In-browser
Price: Free

✅

WCAG 2.1 AA

Tests against WCAG 2.1 Level A and AA standards for complete accessibility compliance.

🎯

ARIA & Labels

Validates ARIA attributes, form labels, and semantic HTML structure.

🔒

100% Private

Everything runs locally. Your HTML never leaves your device.

Check HTML accessibility online

Paste your HTML code, click Check Accessibility, and review the WCAG 2.1 compliance results with errors, warnings, and suggestions.

HTML Code

Options

Fetch from URL (optional)

Demo fetch uses a CORS-friendly approach only if the target allows it.

Privacy-first

This page processes content locally in your browser (no upload).

What is HTML Accessibility Checking?

HTML accessibility checking is the process of testing HTML code against WCAG 2.1 (Web Content Accessibility Guidelines) standards to ensure your website is usable by everyone, including people with disabilities. Our free HTML accessibility checker analyzes your code to detect accessibility barriers that prevent users with visual, auditory, motor, or cognitive disabilities from accessing your content. This html accessibility checker browser tool helps you check HTML code accessibility instantly.

When you build websites, it's essential to ensure they're accessible to all users. Missing alt text on images prevents screen reader users from understanding images. Missing form labels make forms unusable for assistive technology users. Improper heading hierarchy confuses screen reader navigation. Our html accessibility checker for developers helps you identify and fix these issues to achieve WCAG 2.1 AA compliance, which is often required by law and essential for inclusive web design. Check HTML accessibility before deployment to ensure compliance. For more HTML tools, explore our HTML Tools collection.

Feature	Inaccessible HTML	Accessible HTML
Screen Reader Compatibility	Screen readers break, missing alt text, improper headings, no ARIA labels	Screen readers work perfectly, descriptive alt text, proper heading hierarchy, ARIA labels
Keyboard Navigation	Keyboard users can't navigate, missing focus indicators, trapped focus	Full keyboard navigation, visible focus indicators, logical tab order
WCAG Compliance	Fails WCAG 2.1 Level A, legal compliance risk, accessibility barriers	WCAG 2.1 AA compliant, legal compliance, accessible to all users
Legal Compliance	ADA violations, Section 508 non-compliance, potential lawsuits	ADA compliant, Section 508 compliant, reduced legal risk
SEO Impact	Poor crawlability, missing semantic structure, lower rankings	Better crawlability, semantic structure, improved rankings
User Experience	Excludes users with disabilities, poor usability, frustration	Inclusive design, usable by everyone, positive experience

✗Invalid HTML

<!DOCTYPE html>
<html>
<head>
  <title>Example</title>
</head>
<body>
  <h1>Welcome</h1>
  <p>This paragraph is not closed
  <img src="image.jpg">
  <a href="link.html">Click here
</body>
</html>

Missing closing tags, missing alt text, unclosed elements

✓Valid HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Example</title>
</head>
<body>
  <h1>Welcome</h1>
  <p>This paragraph is closed.</p>
  <img src="image.jpg" alt="Description">
  <a href="link.html">Click here</a>
</body>
</html>

All tags closed, proper structure, accessibility attributes

What Does HTML Validation Check?

•Syntax Errors: Missing closing tags, mismatched tags, invalid characters, and malformed HTML structure
•Required Elements: DOCTYPE declaration, html tag, head tag, title tag, body tag, and other essential HTML5 elements
•Accessibility Issues: Missing alt text on images, missing lang attribute, improper heading hierarchy, missing ARIA labels, and other WCAG compliance issues
•SEO Problems: Missing meta description, missing Open Graph tags, improper heading structure, missing title tag, and other SEO best practices
•Performance Warnings: Missing lazy loading on images, oversized images, missing optimization attributes, and other performance issues
•Security Issues: External links missing rel="noopener", insecure resources, and other security best practices

According to W3C WCAG 2.1 guidelines, accessible HTML is the foundation of inclusive web content. Missing alt text, improper heading hierarchy, and missing ARIA labels break screen readers, cause navigation issues, and create barriers for users with disabilities. Our HTML accessibility checker tests for WCAG 2.1 Level A and AA compliance to ensure your website is accessible to everyone.

Modern web development workflows should include HTML accessibility checking as a standard step. Whether you're building a new website, maintaining existing code, or learning HTML, using an HTML accessibility checker helps ensure your code is accessible, legally compliant, and usable by all users. For more information on accessibility standards, see the W3C WCAG 2.1 guidelines, MDN Accessibility documentation, and Google's accessibility guide.

HTML Validation Impact

Real data showing the importance of validating HTML code

85%

Websites Have HTML Errors

According to W3C validation studies

30%

Accessibility Issues

Caused by invalid HTML

25%

SEO Impact

From HTML validation errors

40%

Browser Compatibility

Issues from invalid HTML

📊

Validation Statistics

According to W3C accessibility research, over 98% of websites have accessibility barriers that prevent users with disabilities from accessing content. Missing alt text, improper heading hierarchy, missing form labels, and keyboard navigation issues are common problems. Regular HTML accessibility checking helps catch and fix these issues to achieve WCAG 2.1 compliance and ensure your website is accessible to everyone.

Why Check HTML Accessibility?

Checking HTML accessibility is essential for building inclusive, legally compliant, and user-friendly websites. Our html accessibility checker online free tool helps you check HTML accessibility online quickly. Here's why you should make accessibility checking part of your development workflow:

✅

Ensure Browser Compatibility

Invalid HTML can render differently across browsers. Chrome, Firefox, Safari, and Edge may handle errors inconsistently, leading to layout breaks, missing content, or broken functionality. Valid HTML ensures consistent rendering across all browsers and devices, reducing cross-browser testing time and user complaints.

♿

Improve Accessibility

Inaccessible HTML breaks screen readers and assistive technologies. Missing alt text prevents screen reader users from understanding images. Improper heading hierarchy confuses navigation for users with screen readers. Missing ARIA labels and form labels make interactive elements unusable. Use our wcag 2.1 compliance checker online to test your HTML. Accessible HTML with proper semantic structure, ARIA attributes, and keyboard navigation is the foundation of WCAG 2.1 compliance. This is not just best practice—it's often a legal requirement under ADA, Section 508, and similar laws worldwide.

🎯

Boost SEO Rankings

Search engines like Google prefer valid, well-structured HTML. Missing meta tags, improper heading hierarchy, and invalid structure can hurt your search rankings. Valid HTML with proper semantic structure helps search engines understand and index your content better, potentially improving your rankings and organic traffic.

🐛

Catch Errors Early

HTML validation catches errors before they cause problems in production. Missing closing tags, invalid attributes, and structural errors can lead to broken layouts, JavaScript failures, and user experience issues. Validating during development saves debugging time and prevents costly fixes after deployment.

⚡

Improve Performance

Invalid HTML can cause browsers to spend extra time parsing and fixing errors, slowing down page rendering. Valid HTML renders faster, improving Core Web Vitals metrics like First Contentful Paint (FCP) and Largest Contentful Paint (LCP). Faster pages provide better user experience and can improve search rankings.

🔒

Enhance Security

Valid HTML helps prevent security vulnerabilities. Missing rel="noopener" on external links can expose your site to tabnabbing attacks. Invalid HTML can also make your site more vulnerable to XSS attacks. Validating HTML helps ensure you're following security best practices and protecting your users.

How It Works

Our html accessibility checker browser tool uses client-side parsing and WCAG 2.1 rule checking to check HTML accessibility online. This html accessibility validation tool online works instantly. Here's how the accessibility checking process works:

1

Parse HTML Structure

The validator parses your HTML code to identify all tags, attributes, and structure. It builds a tree representation of your document and checks for proper nesting and hierarchy.

2

Check Syntax Errors

The validator checks for missing closing tags, mismatched tags, invalid attributes, missing required elements (DOCTYPE, html, head, body, title), and other syntax errors that break HTML validity.

3

Validate Accessibility

The validator checks for accessibility issues including missing alt text on images, missing lang attribute, improper heading hierarchy (h1 should be first, no skipped levels), missing ARIA labels, and other WCAG compliance issues.

4

Check SEO & Performance

The validator checks for SEO issues (missing meta description, missing Open Graph tags, improper heading structure) and performance warnings (missing lazy loading, security issues with external links). It generates a comprehensive report with errors, warnings, and suggestions.

Best Practices for HTML Validation

Follow these best practices to ensure your HTML code is valid, accessible, and optimized. Our html accessibility checker instant tool helps you check html for accessibility issues quickly. Use this html accessibility test tool regularly to maintain WCAG compliance:

1

Always Include DOCTYPE

Every HTML document should start with <!DOCTYPE html>. This tells browsers which HTML version to use and ensures proper rendering. Without it, browsers may enter quirks mode, causing inconsistent rendering.

✅ DO: <!DOCTYPE html>
❌ DON'T: Skip DOCTYPE declaration

2

Close All Tags Properly

Every opening tag must have a corresponding closing tag (except self-closing tags like <img>, <br>). Mismatched or unclosed tags can break layout and functionality.

Test regularly: Validate HTML after major changes, before deployment, and as part of your build process

3

Use Semantic HTML

Use semantic HTML5 elements like <header>, <nav>, <main>, <section>, <article>, and <footer>. These improve accessibility, SEO, and code maintainability.

Semantic benefits: Better accessibility • Improved SEO • Easier maintenance • Clearer code structure

4

Add Accessibility Attributes

Always include alt attributes on images, lang attribute on html tag, proper heading hierarchy (h1 → h2 → h3), and ARIA labels where needed. These are required for WCAG 2.1 compliance.

Accessibility checklist: Alt text on images • Lang attribute • Proper headings • ARIA labels • Keyboard navigation

5

Include Essential Meta Tags

Add essential meta tags for SEO and functionality: charset, viewport, description, and Open Graph tags for social sharing. These improve SEO rankings and user experience.

Essential meta tags: charset="UTF-8" • viewport for mobile • description for SEO • og:tags for social

6

Validate Regularly

Validate your HTML code regularly—after major changes, before deployment, and as part of your build process. Use automated validation in CI/CD pipelines to catch errors early. Regular validation prevents issues from accumulating and becoming harder to fix.

Validation schedule: After code changes • Before deployment • In CI/CD pipeline • During code reviews

Frequently Asked Questions

How do I validate HTML code?

Paste your HTML code into the validator, click Validate, and review the results. The tool checks for syntax errors, missing tags, accessibility issues, SEO problems, and performance warnings. All validation happens locally in your browser for complete privacy.

What HTML errors does the validator detect?

Our HTML validator detects missing DOCTYPE, unclosed tags, mismatched closing tags, missing required elements (html, head, body, title), invalid attributes, and structural issues. It also checks for accessibility problems like missing alt text and SEO issues like missing meta tags.

Do you store my HTML code?

No. This HTML validator processes everything locally in your browser. Your code never leaves your device, ensuring complete privacy and security. No server uploads, no data storage, no privacy concerns.

What's the difference between errors and warnings?

Errors are critical issues that break HTML validity or functionality (missing closing tags, invalid structure). Warnings are important but non-critical issues (missing alt text, missing meta tags). Suggestions are best practices for better SEO, accessibility, and performance.

Does this validator check for accessibility issues?

Yes. Our HTML validator checks for accessibility issues including missing alt text on images, missing lang attribute, improper heading hierarchy, missing ARIA labels, and other WCAG compliance issues. This helps ensure your HTML is accessible to all users.

Can I validate HTML from a URL?

Yes. You can fetch HTML from a URL using the fetch feature, though it may be blocked by CORS policies. Alternatively, copy the HTML source code from your browser's developer tools and paste it into the validator for complete validation.

What SEO issues does the validator check?

The validator checks for missing meta description, missing Open Graph tags, improper heading hierarchy (h1 should be first, no skipped levels), missing title tag, and other SEO best practices. These checks help improve your search engine rankings.

Is this checker based on official WCAG standards?

Yes. Our HTML accessibility checker follows official WCAG 2.1 guidelines from the W3C. It checks for compliance with Level A and AA requirements, including proper alt text, language declaration, heading hierarchy, form labels, keyboard navigation, and semantic HTML structure according to WCAG 2.1 standards.

How do I fix HTML accessibility errors?

Review the accessibility report to identify errors. Common fixes include: adding alt text to images, adding lang attribute to html tag, fixing heading hierarchy (h1 → h2 → h3), adding form labels, adding ARIA labels where needed, and ensuring keyboard navigation. Our checker provides specific WCAG guideline references and suggestions for each error to help you fix them quickly.

What's the difference between accessibility checker and validator?

An HTML validator checks code against W3C standards for syntax errors and structural issues. An HTML accessibility checker focuses specifically on WCAG 2.1 compliance—testing for accessibility barriers like missing alt text, improper heading hierarchy, missing ARIA labels, form label issues, and keyboard navigation problems. Our tool combines both validation and accessibility checking for comprehensive testing.

Can I check HTML accessibility automatically?

Yes. You can integrate HTML accessibility checking into your development workflow using CI/CD pipelines, pre-commit hooks, or build tools. For quick checking, our free online HTML accessibility checker provides instant results without any setup. Check HTML accessibility before deployment to catch issues early and maintain WCAG 2.1 compliance.

Why is HTML accessibility important for SEO?

Accessible HTML helps search engines understand and index your content better. Proper heading hierarchy, semantic HTML, alt text, and ARIA labels improve crawlability and indexing. Google also considers accessibility as a ranking factor. Accessible HTML with proper structure improves SEO rankings and organic traffic while ensuring your site is usable by everyone.