CSS Baseline

The CssBaseline component helps to kickstart an elegant, consistent, and simple baseline to build upon.

Global reset

You might be familiar with normalize.css, a collection of HTML element and attribute style-normalizations.

import * as React from 'react';
import CssBaseline from '@mui/material/CssBaseline';

export default function MyApp() {
  return (
    <React.Fragment>
      <CssBaseline />
      {/* The rest of your application */}
    </React.Fragment>
  );
}

Scoping on children

However, you might be progressively migrating a website to Material UI, using a global reset might not be an option. It's possible to apply the baseline only to the children by using the ScopedCssBaseline component.

import * as React from 'react';
import ScopedCssBaseline from '@mui/material/ScopedCssBaseline';
import MyApp from './MyApp';

export default function MyApp() {
  return (
    <ScopedCssBaseline>
      {/* The rest of your application */}
      <MyApp />
    </ScopedCssBaseline>
  );
}

⚠️ Make sure you import ScopedCssBaseline first to avoid box-sizing conflicts as in the above example.

Approach

Layout

box-sizing is set globally on the <html> element to border-box. Every element—including *::before and *::after are declared to inherit this property, which ensures that the declared width of the element is never exceeded due to padding or border.

Scrollbars

:::error This API is deprecated. Consider using color-scheme instead. :::

The colors of the scrollbars can be customized to improve the contrast (especially on Windows). Add this code to your theme (for dark mode).

import darkScrollbar from '@mui/material/darkScrollbar';

const theme = createTheme({
  components: {
    MuiCssBaseline: {
      styleOverrides: (themeParam) => ({
        body: themeParam.palette.mode === 'dark' ? darkScrollbar() : null,
      }),
    },
  },
});

Be aware, however, that using this utility (and customizing -webkit-scrollbar) forces macOS to always show the scrollbar.

Color scheme

This API is introduced in @mui/material (v5.1.0) for switching between "light" and "dark" modes of native components such as scrollbar, using the color-scheme CSS property. To enable it, you can set enableColorScheme=true as follows:

<CssBaseline enableColorScheme />

// or

<ScopedCssBaseline enableColorScheme >
  {/* The rest of your application using color-scheme*/}
</ScopedCssBaseline>

Typography

No base font-size is declared on the <html>, but 16px is assumed (the browser default). You can learn more about the implications of changing the <html> default font size in the theme documentation page.
Set the theme.typography.body1 style on the <body> element.
Set the font-weight to theme.typography.fontWeightBold for the <b> and <strong> elements.
Custom font-smoothing is enabled for better display of the Roboto font.

Customization

Head to the global customization section of the documentation to change the output of these components.