CSS

change br height

// Use this instead of <br> so you can use css to change height:
/* The best spacer ever invented */
hr.space-1 {
  background: transparent;
  color: transparent;
  margin: 0;
  border-style: none;
  height: 1vw;
}
<hr class="space-1">

change br line height

You can't change the height of the br tag itself, as it's not an element that takes up space in the page. It's just an instruction to create a new line.

You can change the line height using the line-height style. That will change the distance between the text blocks that you have separated by empty lines, but natually also the distance between lines in a text block.

For completeness: Text blocks in HTML is usually done using the p tag around text blocks. That way you can control the line height inside the p tag, and also the spacing between the p tags.

how to reduce or increase br tag height in css

br { content: ""; display: block; margin: 1rem 0; }
br::after { content: "› "; /* content: " " space ignored */; float: left; margin-right: 0.5rem; }