CSS z-index

CSS z-index is a property that controls the stacking order of positioned elements on a web page. It specifies the z-axis position of an element, determining whether it appears in front of or behind other elements on the same stacking context.

The z-index property is only applicable to elements that have a position value other than static. Commonly used position values include relative, absolute, fixed, and sticky.

Here’s the syntax for the z-index property:

z-index: value;

• value: The z-index value can be either a positive or negative integer, or the keyword auto. Positive integers bring the element closer to the front, while negative integers push the element further back. The auto value is the default, and elements with z-index: auto will follow their natural stacking order based on their position in the HTML document.

Higher z-index values take precedence over lower values, meaning an element with z-index: 2 will be positioned in front of an element with z-index: 1.

Example:

.first-element {
  position: relative;
  z-index: 2;
}

.second-element {
  position: relative;
  z-index: 1;
}

In this example, .first-element will be stacked in front of .second-element because it has a higher z-index value.

Keep in mind the following considerations when using z-index:

1. z-index only affects elements within the same stacking context. Elements with different stacking contexts, such as those with position: fixed, will not be affected by the z-index of other elements.
2. Children of an element with a specific z-index will inherit that value by default. You can explicitly set a different z-index for child elements to change their stacking order within the parent’s stacking context.
3. If two elements have the same z-index, the one that appears later in the HTML document will be stacked on top (later elements have a higher stacking order).

Using z-index strategically can help you control the visual hierarchy of elements and control how they overlap and interact with each other on your web page. However, excessive use of high z-index values can lead to complex and challenging-to-maintain stacking orders, so it’s essential to use it judiciously.