Why should I use em, and not % for fonts?

The main reason for using em or percentages is to allow the user to change the text size without breaking the design. If you design with fonts specified in px, they do not change size (in IE 6 and others) if the user chooses text size - larger.

1. What is the benefit of using em value for font size?
2. Why should you use em instead of px?
3. Should I use REM or em or px?
4. Should I use em or VW?

What is the benefit of using em value for font size?

Ems do not have fixed sizes. They are scalable, and for that reason ems are good for mobile web development. Ems are relative to the font size set in the CSS. If you don't have one set in the CSS, then 1 em will usually be equal to 16px, which is usually the default font size in browsers.

Why should you use em instead of px?

PX units ensure consistent results even if that's not ideal. EM is relative to the parent element's font size, so if you wish to scale the element's size based on its parent's size, use EM.

Should I use REM or em or px?

Within CSS, em and rem are both scalable units that also specify values of properties. em and rem meet web accessibility standards, and, unlike px , scale better. Consequently, they are more suited for responsive design.

Should I use em or VW?

Use em or rem for things like: font-size, padding, margin. Use % for width or height of containers, divs, or other large components. Use vh and vw to size sections as a percentage of the screen size (for example, I use this a lot to force sections with background images to be full-screen (vh) and/or full-width (vw))