Understanding em vs px in CSS Breakpoints
In CSS media queries, both em and px units can be used to define breakpoints, but they behave differently. The key difference lies in how they scale — px represents absolute pixel values, while em is a relative unit based on the root font size. Using em allows for more flexible, scalable breakpoints that adjust when the base font size changes.
pxbreakpoints are fixed and remain constant regardless of the user’s font or zoom settings.embreakpoints are relative to the root font size (usually 16px by default) and scale when the font size changes.Using
emmakes designs more accessible and responsive to user zoom preferences.pxvalues are easier to reason about but less adaptable to dynamic or user-defined font scaling.
In this example, both breakpoints target the same width (768px), but the em version adapts if the root font size changes — for example, due to user accessibility settings or browser zoom levels. This makes em-based breakpoints more flexible for responsive, user-friendly design.