Understanding z-index in CSS
The z-index property in CSS controls the stacking order of elements along the z-axis (front-to-back). Elements with a higher z-index appear in front of elements with a lower value.
z-indexonly applies to elements that have apositionvalue other thanstatic(relative,absolute,fixed, orsticky).Elements with
position: staticignorez-indexvalues.The stacking context can also be influenced by properties like
opacity,transform,filter,flex, andgrid.Positive values bring elements forward, negative values push them backward.
Default
z-indexisauto, meaning elements follow the natural HTML order unless a stacking context is created.
In this example, box2 overlaps box1 because it has a higher z-index. Using z-index effectively requires understanding the positioning and stacking context of elements.
Always set a
positionother thanstaticwhen usingz-index.Use
z-indexsparingly to avoid complex stacking issues.Combine with grouping elements in containers to manage stacking contexts.
Test overlapping elements across different screen sizes and devices.
Remember that certain CSS properties (like
transform) create new stacking contexts, affectingz-indexbehavior.