CSS - :valid

Example1

This example presents a simple form that colors elements green when they validate and red when they don't.

HTML Content

<form>
  <label>Enter a URL:</label>
  <input type="url" />
  <br />
  <br />
  <label>Enter an email address:</label>
  <input type="email" required/>
</form>

CSS Content

input:invalid {
  background-color: #ffdddd;
}

form:invalid {
  border: 5px solid #ffdddd;
}

input:valid {
  background-color: #ddffdd;
}

form:valid {
  border: 5px solid #ddffdd;
}
  
input:required {
  border-color: #800000;
  border-width: 3px;
}

input:required:valid {
  border-color: #008000;
}