The Full WHATWG HTML RD2301 DTD, like former versions, is a transcription of WHATWG's HTML Review Draft specification prose published January 16th, 2023, into an SGML DTD. The Full DTD covers all elements of HTML, SVG, MathML, and the ARIA attributes, and its construction is described in the reference for the W3C HTML 5 DTD, with only modifications for the current version described in this document.
The Minimal WHATWG HTML RD2301 DTD, also like former versions, is a compact DTD containing only essential parsing rules for HTML. As only HTML's special rules for HTML void elements and enumerated attributes are included (others being admitted freely), the Minimal WHATWG HTML's DTD usefulness for validation purposes is limited. Instead, the purpose of the Minimal HTML DTD is to provide a minimal bundled declaration set for content parsing and production tasks for modern and idiomatic HTML in sgmljs.net and other SGML software with support for resolving declaration sets via catalog resolution.
Note this is an experimental DTD reflecting current HTML
specification work but hasn't seen wide review. Going by the points
mentioned in these release notes, there are in fact at
least two known issues regarding the hidden attribute and the
changed content model of the hgroup element, but also further
incompatible changes related to the legend and param elements
(see below).
The DTD based on the previous HTML Review Draft 200129 remains thus
the recommended version, and the version resolved via about:legacy-compat
in sgmljs.net SGML.
Changed the content model/inclusion constraint for hgroup
(see initial comments about the so-called outlining algorithm),
legend (again), and summary.
Removed the usemap attribute on the object element (again),
and changed the content model of the object element, part of
which involves removal of the param element from WHATWG HTML.
As a consequence, and in line with other removals of elements
allowing tag omission, the param element is now included as
legacy element.
Note changed prose for tag omission rules and/or prohibited
child content on the body and a element without material change
to element declarations are reflected in comments only.
Added event handler attributes onbeforeinput, onbeforematch, oncontextlost,
oncontextrestored, andonscrollend`.
Added global attribute inert.
Removed event handler attribute onabort.
The changed rules for the hidden attribute (applicable to any HTML
element) which, no longer being a "HTML Boolean attribute" but
an enumerated attribute with an additional permitted value of
until-found instead, has the consequence that the long-standing
and widely used practice of using attribute name omission with hidden,
as described in eg mdn-hidden and also used within the HTML spec text
itself, is no longer allowed according to sections 2.3.2 Boolean
attributes and 2.3.3 Enumerated attributes. While this is believed
unintentional and the authors of the HTML spec at
https://github.com/whatwg/html may want to revise this change,
it has no consequence for the SGML DTD, since attribute name omission
is applicable to any enumerated attribute/attribute value, and not
just those attributes whose only possible value happens to coincide
with its name as in HTML "Boolean attributes".
Added the disabled and blocking attribute on the link element.
Added the media attribute on the meta element.
Added the blocking attribute on the style element.
Added the width and height attributes on the source and canvas element.
Added the loading attribute on the img element.
Added the blocking attribute on the script element.
Removed the allowpaymentrequest attribute on the iframe element.