How to Fix ‘Cannot read property ‘config’ of undefined’ When Creating an Expo Project

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If you’re diving into mobile app development with React Native and Expo in 2025, you might hit a frustrating roadblock: the error “Cannot read property ‘config’ of undefined”. Don’t worry—you’re not alone! This error has tripped up many developers, and the good news is it’s fixable. In this guide, we’ll walk you through what this error means, why it pops up when creating an Expo project, and how to solve it step-by-step. By the end, you’ll be back to building your app with confidence!

Let’s break it down in simple, beginner-friendly language and make sure your Expo project runs smoothly in 2025.

What Does ‘Cannot read property ‘config’ of undefined’ Mean?

First things first—what’s this error all about? In plain English, it’s your computer saying, “Hey, I’m trying to find something called ‘config,’ but the thing I’m looking at doesn’t even exist!” In tech terms, this is a TypeError in JavaScript, and it happens when the code tries to access a property (config) on an object that’s undefined.

When you see this error while creating an Expo project, it’s usually tied to the Expo tools—like Expo CLI or Expo Router—having trouble reading your project’s setup. It’s like the app is lost and can’t find its map!

Why Does This Error Happen in Expo Projects?

This specific error, “Cannot read property ‘config’ of undefined”, often shows up when you’re setting up a new Expo project and trying to preview it (say, with Expo Go). Based on real-world cases—like the issue reported on Stack Overflow in 2025—it’s linked to a few common culprits. Here’s why it might happen:

1. Expo Router Setup Issues

Expo Router, a popular navigation tool in 2025, relies on a proper configuration to work. If something’s off in your project’s structure or files (like _layout.tsx), the router can’t find its config and crashes.

2. Outdated or Incompatible Packages

The Expo ecosystem moves fast. If you’re using an older version of Expo CLI, Expo Go, or a library like @react-navigation, it might not play nice with the latest setup instructions from 2025.

3. Missing or Broken Dependencies

Sometimes, key files or dependencies (like react-navigation or Expo’s own modules) aren’t installed correctly, leaving gaps that cause this error.

4. Cache Problems

Old cache files from previous builds can confuse Expo, making it think your project is misconfigured even when it’s not.

5. Syntax or File Errors

A tiny typo in a config file (like app.json or _layout.tsx) or a missing import can throw everything off, leading to this undefined mess.

Real Example: The Stack Overflow Case

In early 2025, a developer on Stack Overflow shared their struggle with this exact error. They followed Expo’s official guide (npx create-expo-app@latest), but when they tried to view their app in Expo Go, they got:

(NOBRIDGE) ERROR Warning: TypeError: Cannot read property 'config' of undefined
This error is located at: in BottomTabBar (created by SafeAreaInsetsContext)...

Sound familiar? Their error pointed to the BottomTabBar component from @react-navigation/bottom-tabs. The community jumped in with fixes—some worked, some didn’t—but it gave us a solid starting point to solve this in 2025.

How to Fix ‘Cannot read property ‘config’ of undefined’ in Expo

Let’s get to the fun part—fixing it! Here are practical, step-by-step solutions based on what’s working in 2025. Try them in order until your app is back on track.

Step 1: Clear Your Cache

Old cache files can mess with Expo’s brain. Let’s give it a fresh start.

  • Open your terminal in your project folder.
  • Run these commands:
  expo start --clear

Or, if that doesn’t work:

  rm -rf node_modules && rm -rf .expo && npm cache clean --force && npm install
  • Restart your project with expo start.

This wipes out stale data and reinstalls everything cleanly. Did it work? If not, keep going!

Step 2: Check Your Expo and Navigation Versions

In 2025, Expo and libraries like @react-navigation need to be in sync. Mismatched versions are a common trigger for this error.

  • Check your package.json file. Look for lines like:
  "expo": "^50.0.0",
  "@react-navigation/bottom-tabs": "^6.5.0"
  • Compare them to Expo’s latest recommendations (check docs.expo.dev).
  • Update if needed:
  npx expo install expo@latest @react-navigation/bottom-tabs@latest
  • Run expo start again.

Still seeing the error? Let’s dig deeper.

Step 3: Simplify Your Layout File

The Stack Overflow case hinted at a problem with BottomTabBar, often tied to _layout.tsx (Expo Router’s root layout file). Let’s test it.

  • Open app/_layout.tsx (or create it in the app folder if it’s missing).
  • Replace its contents with this basic version:
  import { View, Text } from 'react-native';
  import { Stack } from 'expo-router';

  export default function Layout() {
    return (
      <Stack>
        <Stack.Screen name="index" />
      </Stack>
    );
  }
  • Save and run expo start.

If this works, your original layout had an issue (maybe a bad import or navigation setup). Gradually add back your navigation code to pinpoint the culprit.

Step 4: Fix Navigation Setup

Since the error often ties to BottomTabBar, let’s ensure your navigation is set up right.

  • Install the necessary packages:
  npx expo install @react-navigation/native @react-navigation/bottom-tabs react-native-screens react-native-safe-area-context
  • Update _layout.tsx to use tabs correctly:
  import { Tabs } from 'expo-router';
  import { View, Text } from 'react-native';

  export default function Layout() {
    return (
      <Tabs>
        <Tabs.Screen name="index" options={{ title: 'Home' }} />
        <Tabs.Screen name="about" options={{ title: 'About' }} />
      </Tabs>
    );
  }
  • Create app/index.tsx with:
  import { View, Text } from 'react-native';

  export default function Home() {
    return <Text>Hello, Expo!</Text>;
  }
  • Run expo start.

This sets up a simple tab navigation. If it works, your issue was in the navigation config.

Step 5: Update Expo Go and CLI

In 2025, Expo Go (the app on your phone) and Expo CLI need to match your project’s SDK. An outdated app can cause weird errors like this.

  • Update Expo CLI:
  npm install -g expo-cli@latest
  • Check your Expo version:
  expo --version
  • Update Expo Go on your phone to the latest version from the App Store or Google Play.
  • Restart with expo start.

Step 6: Patch Expo Router (Advanced Fix)

If all else fails, a 2025 community fix suggests tweaking Expo Router’s code. This is a bit technical, but it worked for some.

  • Open node_modules/expo-router/build/getLinkingConfig.js.
  • Find line ~62 (look for getPathFromState).
  • Change this.config to this?.config (adds a safety check).
  • Save and run expo start.

This tweak prevents the error by checking if this exists before grabbing config. Note: This edit might get overwritten on updates, so consider it a temporary fix.

Preventing This Error in Future Expo Projects

Once you’ve squashed this bug, let’s keep it from coming back. Here’s how to set up Expo projects smoothly in 2025:

  • Start Fresh: Always use npx create-expo-app@latest to get the newest template.
  • Check Docs: Follow Expo’s official setup guide for the latest steps.
  • Keep Updated: Regularly run npx expo install expo@latest to stay current.
  • Test Small: Build your app bit by bit—test after adding navigation or big features.

FAQs About ‘Cannot read property ‘config’ of undefined’

Why does this error mention BottomTabBar?

It’s tied to @react-navigation/bottom-tabs. If your layout or dependencies are off, the tab bar can’t find its config settings.

Can I ignore this error?

Not really—it’ll stop your app from loading properly in Expo Go or simulators.

Does this happen on all platforms?

It’s most common in Expo Go (iOS/Android), but it can pop up in dev builds too if the setup’s wrong.

Is Expo Router required?

No, but it’s the default in 2025 Expo projects. You can skip it and use plain React Navigation if you prefer.

Get Back to Building Your Expo App!

The “Cannot read property ‘config’ of undefined” error might feel like a brick wall, but it’s just a bump in the road. With 2025 tools and these fixes, you can get your Expo project running in no time. Whether it’s clearing the cache, updating packages, or tweaking your layout, one of these steps will work for you.

Have you hit this error before? How did you fix it? Share your story below—I’d love to hear! Now, go fire up that terminal and bring your app to life!

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