center horizontally and vertically in html code example

Example 1: center div horizontally and vertically

.parent {
  position: relative;
}
.child {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
}

Example 2: how to horizontally and vertically center content in css

.container {
  min-height: 100vh; // height of the browser viewport
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}