W3C

HTML 5.2

W3C First Public Working Draft,

4. The elements of HTML

4.1. The root element

4.1.1. The html element

Categories:
None.
Contexts in which this element can be used:
As the root element of a document.
Wherever a subdocument fragment is allowed in a compound document.
Content model:
A head element followed by a body element.
Tag omission in text/html:
An html element’s start tag can be omitted if the first thing inside the html element is not a comment.
An html element’s end tag can be omitted if the html element is not immediately followed by a comment.
Content attributes:
Global attributes
Allowed ARIA role attribute values:
None
Allowed ARIA state and property attributes:
Global aria-* attributes
DOM interface: 
interface HTMLHtmlElement : HTMLElement {};

The html element represents the root of an HTML document.

Authors are encouraged to specify a lang attribute on the root html element, giving the document’s language. This aids speech synthesis tools to determine what pronunciations to use, translation tools to determine what rules to use, and so forth.

It is recommended to keep the usage of attributes and their values defined on the html element to a minimum to allow for proper detection of the character encoding declaration within the first 1024 bytes.

The html element in the following example declares that the document’s language is English. 
<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Swapping Songs</title>
  </head>
  <body>
    <h1>Swapping Songs</h1>
    <p>Tonight I swapped some of the songs I wrote with some friends, who
    gave me some of the songs they wrote. I love sharing my music.</p>
  </body>
</html>