When you use viewport height (vh) to size fonts, the font size is relative to:

1) the font size specified for the body
2) the browser's default font size
3) the size of the font used by its parent element
4) the size of the viewport

Answer :

The font size specified using viewport height (vh) is relative to the size of the viewport. This allows font sizes to be responsive and adjust to the browser window's height, ensuring better scalability and readability across different devices.

Therefore the correct option is 4) the size of the viewport

When you use viewport height (vh) to size fonts, the font size is relative to the size of the viewport. This unit is one of the many ways designers can define font sizes, with the 'vh' unit scaling the size of the font based on the height of the browser window. Since '1vh' is equivalent to 1% of the viewport height, a font size defined as '10vh' would be 10% of the viewport's height. It's essential for designers to remember that viewport units are responsive and adjust dynamically with the changing size of the browser, making them particularly useful for creating scalable and mobile-friendly designs.

Aside from viewport units, fonts can also be sized using pixels (px), percentages (%), ems, rems, and various other units. The choice of unit can impact how text scales across different devices and user settings, such as when users adjust their browser text size for better readability. It is important to test various text sizes to ensure a seamless user experience. As a best practice, web pages should support the user's ability to increase font size by up to 200% without causing layout issues.