<input type="text" required placeholder="I'm required" />
<br />
<input type="text" placeholder="I'm not" />

body {
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  font-family: Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: 1rem;
  line-height: 3.5rem;
}
input {
  font-size: 1.5rem;
  padding: 0.5rem;
  border-radius: 0.5rem;
}
input:required {
  background: orange;
}