//pc端作判斷
<script>
    if (/mobile/i.test(navigator.userAgent)) {
        window.location = 'http://xxxx/mobile.html'
    }
</script>


//移動端端作判斷
<script>
    if(!/mobile/i.test(navigator.userAgent)){
        window.location = 'http://xxxx/pc.html';
    }
</script>


// 萬能指令碼，自動遮蔽 pc
window.addEventListener('DOMContentLoaded', function() {
    if (!((/
 
Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i).test(navigator.userAgent))) {
        document.documentElement.innerHTML = "<p>請使用手機開啟此頁面哦~</p>";
    }
});

注意：放在meta標籤後