An HTML tag used to define the most important headline (or “he’d” in journalistic jargon) of a document.
HTML allows for 6 levels of headlines within a page (H1, H2… H6).
H1 is the most important and carries the most weight with search engines when the page is indexed.
Additional headlines (known as subheads) are labeled in order of importance from H2 down to the least important, H6. While web design best practices dictate that there be only one H1 element per page, there may be multiples of the other elements, generally nested according to importance. For example, one or more H2 tags may appear beneath the H1 tag with additional H3 tags appearing beneath the H2 tags, etc.