What\'s the Difference Between pt and px in CSS, and When Should You Use Each?

Understanding the Distinction between pt and px in CSS

In the realm of CSS, two seemingly interchangeable units of measurement often provoke confusion: pt and px. This article will endeavor to elucidate the fundamental differences between these units and shed light on their appropriate applications.

Myth: px Represents Pixels

Contrary to popular belief, the px unit in CSS does not directly translate to pixels. As explained in the W3C article "EM, PX, PT, CM, IN...", px is an abstract unit designed to bestow a consistent visual appearance across devices and resolutions.

Defining px: A Visual Perspective

The W3C article paints px as a unit that creates a thin line barely perceptible to the human eye. Essentially, 1 px represents a dimension that, if used to draw a horizontal line, would appear as a crisp, sharp edge without any anti-aliasing.

The Elusive Nature of px

The px unit's definition highlights its elusive nature. Its size varies depending on the device and viewing distance. On early CRT monitors, px roughly represented 1/100th of an inch. However, modern devices capable of displaying more detailed images may use px differently to maintain the same visual effect.

pt vs px vs em: When to Use What

The W3C article recommends using px for:

• Setting precise dimensions that need to remain consistent across devices and viewing distances, such as font sizes and element widths.

pt, on the other hand, is best suited for:

• Typography, as it ensures proportions remain the same across devices regardless of font size.

em is particularly useful for:

• Setting relative dimensions, such as paragraph indentation or line spacing, that scale with the text size.

The above is the detailed content of What\'s the Difference Between pt and px in CSS, and When Should You Use Each?. For more information, please follow other related articles on the PHP Chinese website!