css what is relative length unit

In CSS, relative length units are length units measured based on their relationship to other things and have no fixed value. The actual distance measured may change due to other factors not under its control, such as screen resolution, width and height of the visual area, etc.; and, for some relative units, its size will vary depending on the element using that unit. vary from one to another.

The operating environment of this tutorial: windows7 system, css3 version, Dell G3 computer.

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Relative length units

As the name suggests , there is no fixed value for relative units. Their values ​​are relative to some other predefined value or characteristic. Relative units make it easy for us to resize elements appropriately as we can relate the width, height, font size, etc. of the element to some other basic parameters.

These units are generally recommended when you create responsive layouts and are preferred for digital media. Their values ​​can be relative to the font you are using, or to the height and width of the screen view window.

Commonly used relative length units in CSS

1. Em unit

em is a relative font length unit, and its unit length is based on the element Determined by the vertical length of the text. For example: 1em is equivalent to the current font size (font-size attribute), then 2em is equivalent to twice the current font size. If used for other attributes (width, height), it is relative to the font-size of the element itself. It can be used to set width, height, line-height, margin, padding, border and other styles.

2. rem unit

rem is a new relative font length unit in CSS3. Its length is only determined relative to the font size of the root element, that is, the html element. It is essential for mobile pages. Few units of length.

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