Introduction

Material-UI (MUI) provides powerful theming capabilities and a flexible styling system, but improper usage can lead to UI inconsistencies, unexpected style conflicts, and unnecessary re-renders. Issues such as incorrect theme propagation, improper style overrides, and performance overhead from frequent re-renders can make MUI applications difficult to maintain and debug. This article explores common causes of UI rendering issues in Material-UI, debugging techniques, and best practices for optimizing theming and performance.

Common Causes of UI Rendering Issues in Material-UI

1. Styles Not Applying Due to Incorrect Theme Provider Placement

If the `` is not properly placed in the React component tree, styles may not be applied to components.

Problematic Scenario

import { ThemeProvider, createTheme } from "@mui/material/styles";
import Button from "@mui/material/Button";

const theme = createTheme({
  palette: {
    primary: { main: "#ff0000" }
  }
});

function App() {
  return (
    <div>
      <ThemeProvider theme={theme}>
        <Button color="primary">Red Button</Button>
      </ThemeProvider>
    </div>
  );
}

If `` is not wrapped around the entire application, some components may not inherit the theme correctly.

Solution: Wrap the Entire Application with ``

function Root() {
  return (
    <ThemeProvider theme={theme}>
      <App />
    </ThemeProvider>
  );
}

Placing `` at the top level ensures that all components receive the theme correctly.

2. Custom Styles Not Applying Due to CSS Specificity

Styles applied using the `sx` prop or `makeStyles` may be overridden by default MUI styles due to specificity.

Problematic Scenario

const useStyles = makeStyles({
  button: {
    backgroundColor: "#ff0000"
  }
});

function CustomButton() {
  const classes = useStyles();
  return <Button className={classes.button}>Custom Button</Button>;
}

Since MUI applies its styles with higher specificity, custom styles might not override them.

Solution: Use the `sx` Prop or Theme Overrides

function CustomButton() {
  return (
    <Button sx={{ backgroundColor: "#ff0000 !important" }}>
      Custom Button
    </Button>
  );
}

Using the `sx` prop ensures styles apply correctly and take precedence over MUI’s default styles.

3. Performance Bottlenecks Due to Excessive Theme Re-Renders

Creating a theme inside a component without memoization causes unnecessary re-renders.

Problematic Scenario

function ThemedComponent() {
  const theme = createTheme({ palette: { primary: { main: "#1976d2" } } });

  return (
    <ThemeProvider theme={theme}>
      <Button color="primary">Primary Button</Button>
    </ThemeProvider>
  );
}

The theme object is recreated on every render, causing unnecessary UI updates.

Solution: Memoize the Theme Using `useMemo`

function ThemedComponent() {
  const theme = React.useMemo(() => createTheme({ palette: { primary: { main: "#1976d2" } } }), []);

  return (
    <ThemeProvider theme={theme}>
      <Button color="primary">Primary Button</Button>
    </ThemeProvider>
  );
}

Using `useMemo` ensures the theme object is not recreated unnecessarily.

4. Inconsistent Styling Due to Multiple `` Instances

Defining multiple `` instances in the component tree can cause inconsistent styling.

Problematic Scenario

function App() {
  return (
    <ThemeProvider theme={theme1}>
      <ComponentA />
      <ThemeProvider theme={theme2}>
        <ComponentB />
      </ThemeProvider>
    </ThemeProvider>
  );
}

Nested `` instances can override expected styles and cause inconsistencies.

Solution: Use a Single `` at the Root

function Root() {
  return (
    <ThemeProvider theme={theme}>
      <App />
    </ThemeProvider>
  );
}

Ensuring that only one `` exists prevents unexpected theme overrides.

Best Practices for Optimizing Material-UI Styling and Performance

1. Place `` at the Root Level

Ensure all components receive the same theme by wrapping the entire app.

Example:

<ThemeProvider theme={theme}>
  <App />
</ThemeProvider>

2. Use `sx` Prop for Easier Custom Styling

Prefer `sx` over `makeStyles` for better performance and maintainability.

Example:

<Button sx={{ backgroundColor: "#ff0000 !important" }}>

3. Optimize Theme Performance with `useMemo`

Prevent unnecessary theme re-renders by memoizing theme objects.

Example:

const theme = React.useMemo(() => createTheme(...), []);

4. Avoid Nesting Multiple `` Instances

Use a single theme provider to ensure consistency.

Example:

<ThemeProvider theme={theme}>...</ThemeProvider>

5. Debug Style Conflicts Using the Browser DevTools

Inspect computed styles to identify conflicts and specificity issues.

Example:

right-click → Inspect Element → Computed Styles

Conclusion

Material-UI styling and performance issues often arise from improper theme management, CSS specificity conflicts, excessive re-renders, and inconsistent `` usage. By placing `` at the root, using `sx` for styling, memoizing themes, and avoiding nested theme providers, developers can ensure smooth and efficient MUI applications. Debugging tools and best practices further help maintain a consistent and optimized UI.