An open/visible <details> element:
The open attribute is a boolean attribute.
When present, it specifies that the details should be visible (open) to the user.
The numbers in the table specify the first browser version that fully supports the attribute.
|open||12.0||Not supported||Not supported||6.0||15.0|
The <details> tag is new in HTML5.
In XHTML, attribute minimization is forbidden, and the open attribute must be defined as <details open="open">.