<!-- --------------------- Created By InCoder --------------------- -->
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title></title>
    <link rel="stylesheet" href="main.css">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.1.1/css/all.min.css">
</head>

<body>
    <div class="wrapper">
        <div class="form-input">
            <input type="text" maxlength="20" placeholder="Name" required>
            <i class="fa-solid fa-at"></i>
            <span class="counter"></span>
        </div>
    </div>
</body>

</html>
/* --------------------- Created By InCoder --------------------- */

@import url('https://fonts.googleapis.com/css2?family=Poppins:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&display=swap');

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}

body{
    display: flex;
    height: 100vh;
    align-items: center;
    justify-content: center;
    background-color: #11ca71;
}

.wrapper{
    padding: 2rem 1.6rem;
    border-radius: .2rem;
    background-color: #fff;
}

.wrapper .form-input{
    position: relative;
}

.wrapper input {
    outline: none;
    width: 20rem;
    cursor: text;
    font-size: 1rem;
    position: relative;
    border-radius: .4rem;
    padding: .4rem 1.8rem;
    color: rgb(0 0 0 / 80%);
    transition: all .3s ease-in-out;
    border: 2px solid rgb(0 0 0 / 20%);
}

.wrapper input:focus,
.wrapper input:valid {
    border: 2px solid #11ca71;
}

.wrapper input::placeholder {
    font-weight: 500;
    color: rgb(0 0 0 / 40%)
}

.wrapper .form-input i {
    top: 50%;
    left: 6%;
    z-index: 1;
    position: absolute;
    padding-left: .1rem;
    padding-right: .2rem;
    color: rgb(0 0 0 / 20%);
    transform: translate(-50%, -50%);
}

.wrapper .form-input span {
    right: -8%;
    z-index: 1;
    bottom: -100%;
    position: absolute;
    padding-left: .1rem;
    padding-right: .2rem;
    color: rgb(0 0 0 / 50%);
    transform: translate(-50%, -50%);
}

.wrapper input:valid ~ i {
    color: #11ca71;
}

.wrapper input:valid ~ span {
    color: #11ca71;
}
let input = document.querySelector('.form-input input')
        counter = document.querySelector('.counter')
        maxLength = input.getAttribute('maxlength')
        counter.innerHTML = `${maxLength}/${maxLength}`

        input.addEventListener('keyup', (e) => {
            counter.innerHTML = `${parseFloat(maxLength) - e.target.value.length}/${maxLength}`
        })
Run Pen

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.