# z-index

z-index is the CSS property that helps control layout by providing a third axis to arrange content.

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.