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HTML Validator

Validate HTML markup for common issues.

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Validate HTML markup for common issues.

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Tool guide

HTML Validator Online

Run basic browser-side HTML validation checks for common issues such as missing doctype, mismatched tags, and unclosed tags.

Steps

How it works

  • Paste HTML markup.
  • Run basic validation.
  • Review success or warning messages.
  • Fix issues and validate again.
Highlights

Key features

  • Checks common structural issues.
  • Warns about missing doctype.
  • Does not execute HTML.
  • Provides friendly validation messages.
Use cases

Common uses

  • Review snippets before publishing.
  • Check copied HTML examples.
  • Catch obvious tag mistakes.
Notes

Limitations to know

  • This is not full W3C validation.
  • Advanced semantics and accessibility checks are not included.
  • Some browser parser behavior may differ from production validators.
FAQ

Frequently asked questions

3 answers

Is this full W3C validation?

No. It performs basic browser-only checks for common issues.

Does it run scripts?

No. Input is treated as text.

What issues can it find?

It can warn about missing doctype, mismatched tags, and unclosed tags where practical.