Setting background color for <html> element (without height set to 100%) apply to the whole vi-CodePudding

I found setting background color for entire <html> element (without height set to 100%) result in the whole viewport was set to that color

This html

<!DOCTYPE html>
<html>

<head>
  <style>
  html {
    background-color: green;
    border: 5px dashed white;
    margin : 20px
  }

  body {
    background-color: wheat;
    border: 5px dashed red;
    margin : 20px

  }
  </style>
</head>

<body>  
    1
    <br>
    2
    <br>
    3 
</body>

</html>

will result like this

Obviously, the height of html element is less than the height of viewport, why the background color could extend to whole viewport?

CodePudding user response：

Because the spec says so:

The background of the root element becomes the background of the canvas and covers the entire canvas, anchored (for 'background-position') at the same point as it would be if it was painted only for the root element itself. The root element does not paint this background again.

CodePudding user response：

I guess that's just the browser trying to match colours with the HTMLs background to better blend in. I think it might look weird especially back in the days where most stuff was sized via pixel values.

Extending a browser page wouldn't result in a rough cut of colour where it changes to white or something. But I would guess that's a browserspecific implementation but don't quote me on that.