<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
<style>
input[type="checkbox"] {
-webkit-appearance: none; /* remove default appearance on Webkit-based browsers */
-moz-appearance: none; /* remove default appearance on Mozilla-based browsers */
appearance: none; /* remove default appearance on all other browsers */
width: 20px;
height: 20px;
border: 2px solid #333;
border-radius: 3px;
outline: none;
cursor: pointer;
margin-right: 10px;
}
input[type="checkbox"]:checked:before {
content: "\2714"; /* Unicode checkmark symbol */
display: block;
text-align: center;
font-size: 14px;
line-height: 16px;
color: #fff;
background-color: #333;
border-radius: 2px;
width: 20px;
height: 20px;
}
</style>
</head>
<body>
<input type="checkbox" id="myCheckbox" name="myCheckbox" />
<label for="myCheckbox">Checkbox</label>
</body>