<!doctype html> <meta charset="utf-8"> <title>Reference: overflow:clip doesn't affect the box' own outline</title> <link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1531609"> <style> .outer { width: 50px; height: 50px; margin-left: 100px; margin-top: 100px; background: black; outline: 2px solid grey; } .inner { position: relative; background: blue; height: 100px; width: 100px; opacity: 0.5; } </style> <!-- there should be no overflow --> <div class="outer"> <div class="inner" style="width:50px; height:50px;"></div> </div> <!-- there should be overflow in the vertical dimension, but not horizontally --> <div class="outer"> <div class="inner" style="top:-10px; width:50px"></div> </div> <!-- there should be overflow in the horizontal dimension, but not vertically --> <div class="outer"> <div class="inner" style="left:-30px; height:50px"></div> </div>