Free HTML Validator Online
Validate HTML syntax and check for common errors.
Key Features
✅ Instant Validation
Validate HTML syntax instantly with real-time feedback as you type.
🔍 Common Checks
Detect unclosed tags, missing doctype, duplicate IDs, and more.
⚡ Fast Processing
All operations run locally in your browser for instant results.
🔒 Privacy Protected
Your data never leaves your browser. No server storage.
How to Use HTML Validator
Paste Your HTML Code
Enter or paste your HTML code into the input area.
Click Validate
Press the "Validate" button or let the tool auto-validate as you type.
View the Result
See validation results with error details and warnings in the output area.
Frequently Asked Questions
Basics
What is HTML validation?
HTML validation is the process of checking whether an HTML document follows proper syntax rules and best practices, including correct tag usage, nesting, and structure.
Why should I validate HTML?
Valid HTML ensures consistent rendering across browsers, better accessibility, improved SEO, and easier maintenance of your code.
Common Errors
What are common HTML errors?
Common HTML errors include: unclosed tags, improperly nested elements, missing doctype, duplicate IDs, and deprecated tags.
Is the DOCTYPE declaration required?
While browsers can render HTML without a DOCTYPE, it is required for standards-compliant rendering. Without it, browsers may switch to quirks mode.