Edit in JSFiddle

input {
    display: none;
}
label {
    cursor: pointer;
    display: block;
    border: 1px solid #999;
    border-radius: 11px;
    background-color: #DDD;
    width: 40px;
    height: 20px;
    position: relative;
    transition: all 0.2s;
}
label:after {
    content: '';
    background-color: #FFF;
    border: 1px solid #999;
    border-radius: 10px;
    width: 18px;
    height: 18px;
    position: absolute;
    top: 0;
    left: 0;
    transition: all 0.2s;
}
input:checked + label {
    background-color: #3eafe9;
    border-color: #3eafe9;
}
input:checked + label:after {
    left: 20px;
    border-color: #3eafe9;
}

<input type="checkbox" id="switch" name="some-switch">
    <label for="switch"></label>