What is the purpose of the viewport meta tag?

The purpose of the viewport meta tag is fundamentally linked to creating a responsive web design. This tag helps control the layout and scaling of the webpage on different devices, particularly mobile devices. By using the viewport meta tag, developers can set the width and initial zoom level of the viewport, allowing the design to adapt automatically based on the device's screen size.

For example, when the viewport meta tag is set with content like width=device-width, it ensures that the webpage scales to fit the width of the device being used, making it easier for users to navigate and interact with the website on smaller screens. This adaptability is a core principle of responsive web design, which aims to provide an optimal viewing experience across a variety of devices without the need for separate mobile sites.

Other choices do not pertain to the viewport's function. While specifying character sets, defining document types, and including external scripts are all important aspects of web development, they do not directly influence the responsiveness of a website in the way the viewport meta tag does.