HTML · Document structure

<!doctype html>

Declares standards mode. It must be the very first thing in the document, before <html>.

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Syntax

<!doctype html>

Example

Try it

<!doctype html>
<html lang="en">
  <head><title>Hello</title></head>
  <body><h1>Hello, world.</h1></body>
</html>

Without a doctype the browser falls back to quirks mode and CSS behaves unpredictably.

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