HTML Validator
Free online HTML Validator. Simple, fast, and secure tool running in your browser.
What is the HTML Validator?
The HTML Validator is a core web development tool used to check the markup validity of Web documents in HTML. It inspects your webpage's source code to ensure compliance with W3C standards, catching unclosed tags, missing attributes, or structural errors. Valid HTML is the foundation of an accessible, fast, and SEO-friendly website, ensuring search engine bots can crawl your page and screen readers can interpret your content correctly.
How to Use the HTML Validator
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1
Provide Your HTML
Enter the URL of the webpage to validate, or copy and paste the raw HTML code directly into the input area.
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2
Check Markup
Hit the validate button to initiate a deep scan of your document's structure against modern HTML5 specifications.
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3
Correct Errors
Examine the results line by line. Fix any fatal errors, such as missing closing tags, to ensure a robust page structure.
Frequently Asked Questions
Does invalid HTML affect SEO?
While minor validation errors won't penalize you directly, severe structural errors can prevent search engine crawlers from reading your content correctly, which can drastically hurt your indexing and rankings.
Is HTML validation necessary for accessibility?
Yes, extremely. Assistive technologies, like screen readers, rely on well-formed HTML to convey the structure and content of a page accurately to visually impaired users.