How to Fix “Failed to Compile Web-Vitals” in Your React JS Project

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If you’re working on a React JS project and see the error “failed to compile web-vitals” when you run npm start, don’t panic! It’s a common issue, and I’m here to walk you through fixing it step by step. Whether you’re new to coding or just dipping your toes into React, this guide will make the solution clear and easy to follow. By the end, you’ll know what’s causing the problem, how to fix it, and how to avoid it in the future. Let’s dive in!

What Does “Failed to Compile Web-Vitals” Mean?

Imagine you’re building a cool app with React—a tool that helps you create websites or apps super fast. You type npm start to see your project in action, but instead of your app loading, you get an error about “web-vitals.” What’s going on?

Web-vitals is a tiny library that measures how fast and smooth your app is—like how quickly it loads or how responsive it feels when you click stuff. React projects often include it by default (especially if you used Create React App to set things up). When you see “failed to compile web-vitals,” it means something’s broken with this library, and your project can’t finish building. Don’t worry—it’s fixable!

Here’s why this happens:

  • The web-vitals library might be missing.
  • There’s a typo or mistake in your code.
  • Something’s messed up in your project files.

Let’s figure out how to fix it with some simple steps.

Step 1: Check If Web-Vitals Is Installed

First things first—does your project even have the web-vitals library? It’s like checking if you have all the ingredients before baking a cake.

How to Check

  1. Open your project folder in a code editor (like VS Code).
  2. Find a file called package.json. It’s like a shopping list that tells you what tools your project uses.
  3. Look under "dependencies" or "devDependencies". Do you see "web-vitals" listed? It might look like this:
   "web-vitals": "^3.5.0"

What If It’s Missing?

If you don’t see web-vitals, you need to add it. Open your terminal (that black box where you type commands) and run this:

npm install web-vitals --save-dev
  • npm install: This grabs the library from the internet.
  • --save-dev: Adds it to your project’s “shopping list” as a tool for development.

After it finishes, type npm start again. Did the error go away? If yes, awesome! If not, let’s try the next step.

Step 2: Look at Your Code Imports

Okay, so maybe web-vitals is installed, but your project can’t find it. This happens if your code is looking for something that’s not where it expects it to be—like losing your phone in your room.

Where to Look

In a React project, there’s usually a file called index.js in the src folder. Open it and check for this line:

import reportWebVitals from './reportWebVitals';

This line is like a bridge connecting your app to the web-vitals library. It links to a file called reportWebVitals.js, which uses web-vitals to track performance.

What Could Go Wrong?

  • Missing File: Did you delete reportWebVitals.js by accident? It’s supposed to be in the src folder.
  • Wrong Path: If you moved or renamed that file, the import won’t work.

How to Fix It

If reportWebVitals.js is gone, you can recreate it. Make a new file in the src folder called reportWebVitals.js and paste this:

const reportWebVitals = onPerfEntry => {
  if (onPerfEntry && onPerfEntry instanceof Function) {
    import('web-vitals').then(({ getCLS, getFID, getFCP, getLCP, getTTFB }) => {
      getCLS(onPerfEntry);
      getFID(onPerfEntry);
      getFCP(onPerfEntry);
      getLCP(onPerfEntry);
      getTTFB(onPerfEntry);
    });
  }
};

export default reportWebVitals;

Then, make sure index.js calls it like this:

import reportWebVitals from './reportWebVitals';
reportWebVitals(console.log); // This logs your app’s performance

Run npm start again. Fixed? Sweet! If not, keep reading.

Step 3: Reinstall Everything

Sometimes your project’s files get messy—like a cluttered desk. The node_modules folder (where all your libraries live) might be broken or missing pieces. Let’s clean it up and start fresh.

How to Do It

  1. In your terminal, go to your project folder (use cd your-project-name if you’re not there).
  2. Delete the messy stuff:
   rm -rf node_modules package-lock.json
  • node_modules: The folder with all your libraries.
  • package-lock.json: A file that keeps track of library versions.
  1. Reinstall everything:
   npm install
  1. Test it:
   npm start

This is like hitting the reset button. If web-vitals was corrupted, this should fix the “failed to compile” error.

Step 4: Check for Version Problems

Imagine you’re building a Lego set, but some pieces are from an old kit and don’t fit. That’s what happens if web-vitals, React, or other tools in your project don’t match up.

How to Check Versions

In package.json, look at these lines:

"react": "^18.2.0",
"react-dom": "^18.2.0",
"web-vitals": "^3.5.0"

These numbers show the versions. If they’re super old or mismatched, that could cause the error.

How to Fix It

Update them to the latest versions:

npm install web-vitals@latest react@latest react-dom@latest

Then run npm start. This ensures everything plays nicely together.

Step 5: Dig Deeper If It’s Still Broken

If none of the above worked, it’s time to play detective. The error message in your terminal has clues—let’s use them.

What to Look For

  • Full Error Text: Does it mention a specific line or file? For example, it might say “Module not found” or “Syntax error.”
  • Your Code: Open reportWebVitals.js or other files using web-vitals. Did you typo something? Maybe you wrote webVitals instead of web-vitals.
  • Custom Setup: If you didn’t use Create React App, your project might use tools like Webpack. Check their settings (like webpack.config.js) to make sure they’re not blocking web-vitals.

Example Fix

Here’s a common mistake and how to fix it. If reportWebVitals.js has this:

import { getLCP } from 'webVitals'; // Wrong!

It should be:

import('web-vitals').then(({ getLCP }) => { // Right!
  getLCP(console.log);
});

The library uses “dynamic imports” (a fancy way of loading it on demand), so the syntax matters.

Why Web-Vitals Matters in React

Now that we’re fixing the error, you might wonder: why is web-vitals even in my project? Good question! It’s there to make your app better.

What It Does

  • Speed Check: Measures how fast your app loads (like First Contentful Paint, or FCP).
  • Smoothness: Tracks if buttons and links respond quickly (like First Input Delay, or FID).
  • Stability: Watches if stuff on the screen jumps around (Cumulative Layout Shift, or CLS).

Why You Care

If your app is slow or clunky, people won’t use it. Google also likes fast apps and ranks them higher in search results. So, keeping web-vitals working helps you build something awesome.

How to Avoid This Error Next Time

Prevention is better than fixing, right? Here’s how to keep “failed to compile web-vitals” from popping up again:

  • Don’t Delete Files: Leave reportWebVitals.js alone unless you know what you’re doing.
  • Update Regularly: Run npm update every few months to keep libraries fresh.
  • Read Errors: When something breaks, scroll up in the terminal. The clues are there!

Wrapping Up: You’ve Got This!

The “failed to compile web-vitals” error might feel like a roadblock, but it’s just a bump in your coding journey. By checking if web-vitals is installed, fixing imports, reinstalling dependencies, matching versions, and digging into the error, you’ll get your React project running smoothly again. Next time you type npm start, you’ll see your app—not an error!

Got questions or still stuck? Drop a comment below or search for “React web-vitals error” on sites like Stack Overflow. You’re not alone—tons of coders have faced this and figured it out.

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