Free tool

HTML Validator

Check your HTML code for errors and ensure it follows web standards. Catch problems before your visitors do.

Validate HTML

Validation features

Standards compliance

Check your HTML against W3C web standards

Error detection

Find syntax errors, missing tags, and invalid attributes

Warnings and suggestions

Get recommendations for improving your markup

Line-by-line feedback

See exactly where each issue occurs in your code

What we check

+Tag matching
+Attribute validity
+Nesting rules
+DOCTYPE declaration
+Character encoding
+Required elements
+Deprecated tags
+Accessibility basics

How validation works

Validate your code in 3 steps

1Step 1

Submit your HTML

Upload a file, paste code, or enter a URL to validate.

2Step 2

Review results

See errors and warnings with line numbers and explanations.

3Step 3

Fix and revalidate

Make corrections and run validation again until your code is clean.

Validate HTML

Ready to validate your code?

Check your HTML for errors and publish with confidence.

Start validation