iew.html#doctype-syntax-toc">T</a>
</h2>
    <p>A
    <dfn id="doctype">doctype</dfn>
    (sometimes capitalized as &#8220;DOCTYPE&#8221;) is an special instruction
    which, for legacy reasons that have to do with processing
    modes in browsers, is a required part of any
    <a href="documents.html#syntax-document-html" id="syntax-document-html_xref7">document in the HTML syntax</a>;
    it
    <a href="terminology.html#must-requirement" id="must-requirement_xref12">must</a>
    match the characteristic