<ul data-eligibleForWebStory="true">3 modern ways to center a div using CSS include Flexbox, Grid, and margin auto.Flexbox is reliable for horizontal and vertical alignment, using display: flex and align-items/justify-content.Grid offers a clean solution with display: grid and place-items: center for both horizontal and vertical centering.Margin auto is effective for horizontal centering by setting a fixed width and applying margin: auto.