Font scaling based on width of container using CSS

The font size can be set with vw (viewport) unit, which means the viewport width. The viewport is the browser window size. 1vw = 1% of viewport width. If the viewport is 50cm wide, 1vw is 0.5cm. That way the font size will follow the size of the browser window.

Syntax:

element {
    font-size: #vw;
    // CSS Property
}

Where # is a number relative to the container size.

Example 1:

html

<!DOCTYPE html>
<html>
 
<head>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>Font Scaling</title>
    <style>
        #container {
          display: inline-block;
          background-color: green;
          padding: 0.5vw 1vw;
        }
        .divtext {
          display: table;
          color: white;
          font-family: impact;
          font-size: 4.2vw;
        }
    </style>
</head>
 
<body>
     
    <h1>GeeksforGeeks</h1>
 
    <div id="container">
        <div class="divtext">
            Resize the browser window to see
            how the font size scales.
        </div>
    </div>
</body>
 
</html>

Output:

Example 2: Media queries can be used to change the font size of an element on specific screen sizes.

html

<!DOCTYPE html>
<html>
 
<head>
    <meta name="viewport"
          content="width=device-width, initial-scale=1">
    <title>Font Scaling</title>
    <style>
        h2 {
            text-align: center;
        }
        div.example {
            background-color: lightgreen;
            padding: 20px;
            text-align: center;
        }
        @media screen and (min-width: 601px) {
            div.example {
                font-size: 40px;
            }
            .a{
                font-size: 25px;
                text-align: center;
            }
        }
        @media screen and (max-width: 600px) {
            div.example {
                font-size: 30px;
            }
            .a{
                font-size: 18px;
                text-align: center;
            }
        }
        @media screen and (min-width: 800px) {
            div.example {
                font-size: 60px;
            }
            .a{
                font-size: 35px;
            }
        }
    </style>
</head>
 
<body>
    <div class="example">
        Font size automatically adjusting
        according to the width of the container
    </div>
    <p class="a">
        Change the width of the browser window
        to see the font scaling automatically according to the
        container size.
    </p>
 
</body>
 
</html>