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When to Use style vs sx in Material-UI

Authors
  • Name
    Ripal & Zalak
    Twitter

When Should You Use style Instead of sx in Material-UI?

Material-UI (MUI) provides two main ways to apply styles to components: the style prop and the sx prop. While they may seem similar at first glance, there are key differences in how they function under the hood.

Key Differences Between style and sx

Featurestyle Propsx Prop
Works with HTML elements✅ Yes❌ No (Only MUI components)
Works with MUI components✅ Yes✅ Yes
Supports MUI Theme❌ No✅ Yes
Supports Media Queries❌ No✅ Yes
Supports Nesting❌ No✅ Yes
Pseudo Selectors (:hover, ::after, etc.)❌ No✅ Yes

When to Use style

Use the style prop when:

  • Applying inline styles to standard HTML elements (div, span, h1, etc.).
  • Using dynamic styles that frequently change (e.g., based on component state).
  • Avoiding unnecessary CSS injection into the <head> tag.

Example:

import { useState } from 'react'

function DynamicBox() {
  const [height, setHeight] = useState(50)

  return (
    <div
      style={{
        height: `${height}px`,
        width: '100px',
        backgroundColor: 'blue',
      }}
    />
  )
}

When to Use sx

Use the sx prop when:

  • Styling Material-UI components (Box, Grid, Typography, etc.).
  • Leveraging MUI's theme (theme.palette, theme.spacing, etc.).
  • Adding responsive styles with MUI’s breakpoints.
  • Nesting styles within components.

Example:

import { Box, Typography } from '@mui/material'

function StyledComponent() {
  return (
    <Box
      sx={{
        backgroundColor: 'black',
        h4: {
          color: (theme) => theme.palette.primary.main,
        },
      }}
    >
      <Typography variant="h4">This is a title</Typography>
    </Box>
  )
}

Performance Considerations

One major drawback of using sx for frequently changing styles is that MUI creates new CSS classes in the <head> tag each time a new style value is applied. This can lead to unnecessary style injections and performance issues.

Recommendation:

  • Use style for frequently changing dynamic values.
  • Use sx for static styles, theme-based styles, media queries, and pseudo-selectors.

FAQ

1. Can I use both style and sx together?

Yes, you can use both in the same component. However, try to keep dynamic styles in style and theme-based/static styles in sx.

2. Why does sx not work on standard HTML elements?

The sx prop is a special utility provided by Material-UI that works exclusively with MUI components. Standard HTML elements do not understand the sx syntax.

3. Can I use CSS-in-JS libraries like Emotion instead of sx?

Yes, Material-UI uses Emotion as its default styling engine, so you can use Emotion’s css prop for more customization.