Unknown margin of li elements [duplicate]

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• How to remove the space between inline-block elements? 20 answers

I have a navbar with css but the li elements have 2px margin to left and right, even when I use margin: 0, and I have to use margin: 0px -2px to "fix" it

Here is the original code snippet

ul,
li {
    margin:0;
    padding:0;
}
nav{
    background:#333;
}
nav ul{
    text-align: center;
}
nav ul li{
    display:inline-block;
    list-style:none;
}
nav ul li a{
  background: green;
    color:#fff;
    padding:15px;
    display:block;
    text-decoration:none;
    font-weight:600;
    font-size:16px;
}

<nav>
    <ul>
        <li><a href="#">home</a></li>
        <li><a href="#">home2</a></li>
        <li><a href="#">home3</a></li>
        <li><a href="#">home4</a></li>
    </ul>
</nav>