CodePen

HTML

            
              <div class=outer>
  <fieldset class=inner>
      fooooooooooooooooooooooooooooooooooooo
  </fieldset>
</div>

<div class=outer>
  <div class=inner>
    fooooooooooooooooooooooooooooooooooooooo
  </div>
</div>

            
          
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↑ Insert the most common viewport meta tag

CSS

            
              .outer {
  width: 60px;
}

.inner {
  overflow: auto;
  display: block;
  height: 60px;
  border: 1px solid red;
  min-width: 0;
}
            
          
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JS

            
              
            
          
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