Validators
HTML Validator
Check your HTML code for syntax errors and structural issues. Get real-time feedback with line-by-line diagnostics to ensure your web pages follow modern standards.
Check your HTML code for syntax errors and structural issues. Get real-time feedback with line-by-line diagnostics to ensure your web pages follow modern standards.
Search for a command to run...
Paste your HTML code into the editor input area.
Click the 'Validate HTML' button to start the diagnostic check.
Examine the error list that appears below the editor for syntax warnings.
Click an error message to jump directly to the problematic line in your code.
Fix the indicated issues and re-validate to ensure your markup is perfect.
Did You Know?
Valid HTML improves search engine ranking by making it easier for bots to parse your site's content.
Comprehensive Syntax Analysis: Identifies unclosed tags, misplaced elements, and invalid attributes immediately.
Precise Error Diagnostics: Provides specific line and column numbers for every detected issue in your markup.
Interactive Error Markers: Click on any error message to automatically jump to the corresponding line in the editor.
HTML5 Compliance: Validates your code against modern semantic standards for improved accessibility.
Clean Interface: An IDE-like experience that highlights errors visually as you work through your code.
Best Practice
Always include an alt attribute on img tags to ensure accessibility and pass validation checks.
Search Engine Optimization: Valid HTML makes it easier for search engine bots to crawl and index your content correctly.
Universal Browser Compatibility: Standard-compliant code ensures your website renders consistently across different devices and browsers.
Improved Accessibility: Catching structural errors helps ensure that screen readers can interpret your page for users with disabilities.
Faster Debugging: Quickly pinpoint simple mistakes that could otherwise lead to hours of layout troubleshooting.
Unclosed Tags: Forgetting to close structural elements like <div> or <span> can break the entire page layout.
Invalid Attribute Nesting: Placing block-level elements inside inline elements, which violates standard hierarchy rules.
Duplicate ID Attributes: Using the same ID multiple times on one page, which interferes with CSS styling and JavaScript functionality.
Missing Alternative Text: Omitting alt attributes on images, which is a common failure for accessibility standards.
Tip
Use the HTML Formatter tool before validating to make structural nesting errors easier to spot manually.
Validate Early and Often: Integrate validation into your daily workflow to catch errors before they become difficult to fix.
Clean Before Validating: Use a formatter to organize your code first, making structural issues easier to see.
Check Before Deployment: Always run your final markup through a validator before pushing to a production environment.
Monitor CI/CD Pipelines: Incorporate automated linting and validation steps in your build process for consistent quality.
Q: Does this validator support the latest HTML5 tags? A: Yes, it is updated to support the latest semantic elements and attributes defined in the HTML5 living standard.
Q: Can I validate small snippets instead of full pages? A: Absolutely. You can paste any portion of HTML, from a single component to a complete document.
Q: Why does the validator report an error for my closing tag? A: This usually happens because a parent tag was never properly opened or was closed prematurely, confusing the document structure.
Did You Know?
Duplicate IDs in HTML are invalid and can cause JavaScript functions to fail when selecting elements.
MDN Web Docs: HTML - The most comprehensive guide to HTML elements and attributes.
W3C HTML Specification - The official technical documentation for the HTML standard.
WebAIM: Accessibility Basics - Guidance on creating accessible web content through valid markup.