Answer
No. The HTML tags are not case-sensitive.
The HTML elements are defined by starting with an opening tag, followed by content, and followed by a closing tag.
Example
<h1>Heading</h1>
<p>First paragraph text goes here.</p>
<hr>
<p>Second paragraph text goes here.</p>
In the above example, the elements <h1> <p>, <hr> are all HTML elements, and the element <hr> is a an empty element.