'React + Material-UI - Warning: Prop className did not match

I'm having difficulty with differences between client-side and server-side rendering of styles in Material-UI components due to classNames being assigned differently.

The classNames are assigned correctly on first loading the page, but after refreshing the page, the classNames no longer match so the component loses its styling. This is the error message I am receiving on the Console:

Warning: Prop className did not match. Server: "MuiFormControl-root-3 MuiFormControl-marginNormal-4 SearchBar-textField-31" Client: "MuiFormControl-root-3 MuiFormControl-marginNormal-4 SearchBar-textField-2"

I've followed the Material-UI TextField example docs, and their accompanying Code Sandbox example, but I can't seem to figure out what is causing the difference between the server and client classNames.

I experienced a similar issue when adding Material-UI Chips with a delete 'x' icon. The 'x' icon rendered with a monstrous 1024px width after refreshing. The same underlying issue being that icon was not receiving the correct class for styling.

There are a few questions on Stack Overflow addressing why the client and server might render classNames differently (e.g. need to upgrade to @Material-UI/core version ^1.0.0, using a custom server.js, and using Math.random in setState), but none of these apply in my case.

I don't know enough to tell whether this Github discussion might help, but likely not since they were using a beta version of Material-UI.

Minimal steps to reproduce:

Create project folder and start Node server:

mkdir app
cd app
npm init -y
npm install react react-dom next @material-ui/core
npm run dev

edit package.json:

Add to 'scripts': "dev": "next",

app/pages/index.jsx:

import Head from "next/head"
import CssBaseline from "@material-ui/core/CssBaseline"
import SearchBar from "../components/SearchBar"

const Index = () => (
  <React.Fragment>
    <Head>
      <link
        rel="stylesheet"
        href="https://fonts.googleapis.com/css?family=Roboto:300,400,500"
      />
      <meta name="viewport" content="width=device-width, initial-scale=1" />
      <meta charSet="utf-8" />
    </Head>
    <CssBaseline />
    <SearchBar />
  </React.Fragment>
)

export default Index

app/components/SearchBar.jsx:

import PropTypes from "prop-types"
import { withStyles } from "@material-ui/core/styles"
import TextField from "@material-ui/core/TextField"

const styles = (theme) => ({
  container: {
    display: "flex",
    flexWrap: "wrap",
  },
  textField: {
    margin: theme.spacing.unit / 2,
    width: 200,
    border: "2px solid red",
  },
})

class SearchBar extends React.Component {
  constructor(props) {
    super(props)
    this.state = { value: "" }
    this.handleChange = this.handleChange.bind(this)
    this.handleSubmit = this.handleSubmit.bind(this)
  }

  handleChange(event) {
    this.setState({ value: event.target.value })
  }

  handleSubmit(event) {
    event.preventDefault()
  }

  render() {
    const { classes } = this.props
    return (
      <form
        className={classes.container}
        noValidate
        autoComplete="off"
        onSubmit={this.handleSubmit}
      >
        <TextField
          id="search"
          label="Search"
          type="search"
          placeholder="Search..."
          className={classes.textField}
          value={this.state.value}
          onChange={this.handleChange}
          margin="normal"
        />
      </form>
    )
  }
}

SearchBar.propTypes = {
  classes: PropTypes.object.isRequired,
}

export default withStyles(styles)(SearchBar)

Visit page in browser localhost:3000 and see this:

red border around TextField component

Refresh the browser and see this:

TextField component's styles are gone

Notice that the red border around TextField disappears.

Relevant Libs:

  • "react": 16.4.0
  • "react-dom": 16.4.0
  • "next": 6.0.3
  • "@material-ui/core": 1.2.0
node.jsreactjsmaterial-uinextjs


Solution 1:[1]

This problem is related to MUI using dynamic class name which contain an ID. The IDs from the server side rendered CSS are not the same as the client side CSS, hence the mismatch error. A good start is to read the MUI SSR documentation

If you have this problem with nextjs (as I did) follow the example provided by the MUI team, which can be found here: material-ui/examples/nextjs

The most important part is in "examples/nextjs/pages/_app.js":

componentDidMount() {
    // Remove the server-side injected CSS.
    const jssStyles = document.querySelector('#jss-server-side');
    if (jssStyles) {
      jssStyles.parentElement.removeChild(jssStyles);
    }
  }

the related ticket can be found here: mui-org/material-ui/issues/15073

what it does, is remove the server side rendered stylesheet and replace it by a new client side rendered one

Solution 2:[2]

The issue is the server side generates the class names but style sheets are not automatically included in the HTML. You need to explicitly extract the CSS and append it to the UI for the server side rendered components. The whole process is explained here: https://material-ui.com/guides/server-rendering/

Solution 3:[3]

There is one other important, separate issue here: Material UI V4 is not React Strict Mode compatible. Strict mode compatibility is slated for version 5 with the adoption of the Emotion style engine.

Until then, be sure you disable React Strict Mode. If you're using Next.js, this is turned on by default if you've created your app using create-next-app.

// next.config.js
module.exports = {
  reactStrictMode: false, // or remove this line completely
}

Solution 4:[4]

I had the same problem with Next.js and styled component, with the transpilation by Babel. Actually, the class names are different on the client and the server side.

Fix it in writing this in your .babelrc :

{
"presets": ["next/babel"],
"plugins": [
    [
      "styled-components",
      { "ssr": true, "displayName": true, "preprocess": false }
    ]
]
}

Solution 5:[5]

I met this problem on Material-ui V5. The solution to fix this problem is to make sure that class name generator needs to behave identically on the server and on the client. so adding the code below in your _app.js:

import { StylesProvider, createGenerateClassName } from '@mui/styles';

const generateClassName = createGenerateClassName({
  productionPrefix: 'c',
});

export default function MyApp(props) {
  return <StylesProvider generateClassName={generateClassName}>...</StylesProvider>;
}

Solution 6:[6]

// 1 . Warning: prop classname did not match. Material ui   with   React  Next.js

// 2 . Use your customization  css here
const useStyles = makeStyles((theme) => ({

    root: {
        flexGrow: 1,
    },

    title: {
        flexGrow: 1,
    },
    my_examle_classssss: {
        with: "100%"
    }

}));


// 3 . Here my Component    
const My_Example_Function = () => {

    const classes = useStyles();

    return (
        <div className={classes.root}>
            <Container>
                <Examle_Component>    {/*  !!! Examle_Component  -->  MuiExamle_Component*/}

                </Examle_Component>
            </Container>
        </div>
    );
}

export default My_Example_Function


// 4. Add  name parameter to the makeStyles function   

const useStyles = makeStyles((theme) => ({

    root: {
        flexGrow: 1,
    },

    title: {
        flexGrow: 1,
    },
    my_examle_classssss: {
        with: "100%"
    },
}), { name: "MuiExamle_ComponentiAppBar" });  

{/* this is the parameter you need to add     { name: "MuiExamle_ComponentiAppBar" } */ }


{/* The problem will probably be resolved     if the name parameter matches the first className in the Warning:  you recive..    


EXAMPLE :

    Warning: Prop `className` did not match. 
    Server: "MuiSvgIcon-root makeStyles-root-98" 
    Client: "MuiSvgIcon-root makeStyles-root-1"


The name parameter will be like this   { name: "MuiSvgIcon" }




*/  }

Solution 7:[7]

I like to share this mismatching case:

next-dev.js?3515:32 Warning: Prop className did not match. Server: "MuiButtonBase-root MuiIconButton-root PrivateSwitchBase-root-12 MuiSwitch-switchBase MuiSwitch-colorSecondary" Client: "MuiButtonBase-root MuiIconButton-root PrivateSwitchBase-root-12 MuiSwitch-switchBase MuiSwitch-colorSecondary PrivateSwitchBase-checked-13 Mui-checked"

On client there are two more classes which means that the behavior on client-side is different. In this case, this component shouldn't render on server-side. The solution is to dynamically render this component:

export default dynamic(() => Promise.resolve(TheComponent), { ssr: false });

Solution 8:[8]

I had a problem with different classNames for client and server. I was using React, Material-UI, makeStyles and SSR (server-side rendering). The error was:

Warning: Prop `className` did not match. Server: "jss3" Client: "App-colNav-3"

I spent several hours before I figured out that I had discrepancy in webpack mode for client and server. The scripts in package.json were:

    "devServer": "webpack --config webpack.server.config.js --mode=production --watch",
    "devClient": "webpack --mode=development --watch",

After I changed both to have development mode, the problem was solved :)

    "devServer": "webpack --config webpack.server.config.js --mode=development --watch",
    "devClient": "webpack --mode=development --watch",

Solution 9:[9]

The problem is cause by Nextjs server side rendering. In order to solve I do as following:

  1. Make a component to detect whether is it from Client side
import { useState, useEffect } from "react";

interface ClientOnlyProps {}

// @ts-ignore
const ClientOnly = ({ children }) => {
  const [mounted, setMounted] = useState<boolean>(false);

  useEffect(() => {
    setMounted(true);
  }, []);

  return mounted ? children : null;
};

export default ClientOnly;
  1. Wrap my page component using ClientOnly component
export default function App() {
  return (
    <ClientOnly>
      <MyOwnPageComponent>
    </ClientOnly>
  );
}

So the idea is, if it is client side then only render the component on the page. Therefore if current rendering is from Client side, render <MyOwnPageComponent>, else render nothing

Solution 10:[10]

In my case the issue happened because of different compilation modes of webpack for client-side code and server-side: client's bundle was generated by webpack using "production" mode, while server ran some SSR code from a package optimized for "development". This created a different "className" hash in styled-components in generateAndInjectStyles():

if (process.env.NODE_ENV !== 'production') dynamicHash = phash(dynamicHash, partRule + i);

So my fix was just to align the webpack modes.

Solution 11:[11]

You can add the name in anywhere you use makeStyles, like this:

const useStyles = makeStyles({
  card: {
    backgroundColor: "#f7f7f7",
    width: "33%",
  },
  title: {
    color: "#0ab5db",
    fontWeight: "bold",
  },
  description: {
    fontSize: "1em"
  }
}, { name: "MuiExample_Component" });

I am not sure how it works, but I found it here: Warning: Prop `className` did not match ~ Material UI css arbitrarily breaks on reload

Solution 12:[12]

If somebody is still struggling even after trying above solutions, Try this

  • If you have used noSsr prop in any of your components or theme, then remove it.

I had the following config in mui theme object, which was causing this problem.

import { createTheme, responsiveFontSizes } from "@mui/material/styles";
let theme = createTheme({
  components: {
    MuiUseMediaQuery: {
      defaultProps: {
        noSsr: true,
      },
    },
  },
  palette: {
    mode: "light",
    common: {
      black: "#000",
      white: "#fff",
    },
    primary: {
      main: "#131921",
      contrastText: "#fff",
    },
    secondary: {
      main: "#fb6a02",
      contrastText: "#fff",
    }
   }
})
  • RemovingnoSSr fixed all of the issues in my app including style mismatch between client and server.

Solution 13:[13]

I'm also using NextJS + MUI v5 and I ran into this exact error right after merging Git branches. I suspect the merge corrupted something in the cache. I deleted the contents of .next/ and restarted the dev server and the error went away.

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