<pre>\newline ignored in HTML

To make it easier to author documents in plain text

A single newline may be placed immediately after the start tag of pre and textarea elements. This does not affect the processing of the element. The otherwise optional newline must be included if the element's contents themselves start with a newline (because otherwise the leading newline in the contents would be treated like the optional newline, and ignored).

HTML Living Standard

Try it yourself, add newline with Shift+Enter:

^ add newline

<pre> instantiated from outerHTML:

^ add newline

Unfortunately this makes leading newline to be destroyed on live authoring save-load cycle. Fixed in XHTML.