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docs/data/material/customization/z-index/z-index.md

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+# z-index
+
+<p class="description">z-index is the CSS property that helps control layout by providing a third axis to arrange content.</p>
+
+Several Material UI components utilize `z-index`, employing a default z-index scale
+that has been designed to properly layer drawers, modals, snackbars, tooltips, and more.
+
+The `z-index` values start at an arbitrary number, high and specific enough to ideally avoid conflicts:
+
+- mobile stepper: 1000
+- fab: 1050
+- speed dial: 1050
+- app bar: 1100
+- drawer: 1200
+- modal: 1300
+- snackbar: 1400
+- tooltip: 1500
+
+These values can always be customized.
+You will find them in the theme under the [`zIndex`](/material-ui/customization/default-theme/?expand-path=$.zIndex) key of the theme.
+Customization of individual values is discouraged; should you change one, you likely need to change them all.