HTML Validator
Check your HTML code for common errors, warnings, and best practice issues.
Features
Comprehensive HTML validation right in your browser.
Tag Validation
Detects unclosed tags, deprecated elements like <font> and <marquee>, and empty tags that may indicate incomplete markup.
Accessibility Checks
Ensures all <img> elements have alt attributes and the <html> tag includes a lang attribute for screen readers.
Duplicate ID Detection
Finds duplicate ID attributes in the document which cause JavaScript and CSS selector issues.
Instant Validation
Get results in milliseconds with zero uploads. Validate as fast as you can type.
How It Works
Three simple steps to validate your HTML.
Paste Your HTML
Enter or paste your HTML code into the input textarea. Full documents or fragments are both supported.
Click Validate
Hit the Validate button to parse your HTML and run all checks for errors and warnings.
Review Results
See a summary of tags, elements, and issues. Each problem is listed with severity and a clear description.
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Frequently Asked Questions
Common questions about HTML validation.
What does the HTML Validator check for?
It checks for missing DOCTYPE, missing title, missing charset, unclosed tags, deprecated elements (font, center, marquee, etc.), missing alt attributes on images, duplicate IDs, empty elements, and missing lang attribute on the html element.
Is this the same as the W3C Validator?
No. The W3C Validator performs full spec-compliant validation against the HTML standard. This tool focuses on the most common and impactful issues that affect accessibility, SEO, and code quality. It runs entirely in your browser and is much faster for quick checks.
Is my HTML code sent to a server?
No. Your HTML is validated locally and never uploaded. Safe to use with any code including unreleased projects.
Can I validate partial HTML fragments?
Yes. You can paste a full HTML document or just a fragment. For fragments, you may see warnings about missing DOCTYPE, title, or charset — these are expected since they would normally be in the full document.