Fix Expo Heap Memory

This one bit me in a large Expo app, bundling died mid-way. Here’s the exact fix that saved me time.

While developing a large React Native app using Expo, I ran into a crash that looked like this:

Android Bundling failed 29201ms node\_modules/expo-router/entry.js (2156 modules)
ERROR global.css: A jest worker process (pid=4320) was terminated by another process: signal=SIGTERM

This usually means that the Node.js process was killed due to out-of-memory conditions, especially during heavy bundling in complex projects, tracing this out took an eternity.

Checking Current Node Heap Size

Before changing anything, check how much heap memory Node is using:

node -e "console.log((require('v8').getHeapStatistics().heap_size_limit / 1024 / 1024).toFixed(2) + ' MB')"

If it prints something around 2096.00 MB, then you're hitting the ~2GB default heap limit.

Increasing Heap Size (Linux/macOS - Zsh or Bash)

To temporarily increase heap size for the current terminal session:

export NODE_OPTIONS="--max_old_space_size=4096"

Then start your Expo app:

npx expo start

To make this permanent, add the export line to your shell config:

• For Zsh:

  echo 'export NODE_OPTIONS="--max_old_space_size=4096"' >> ~/.zshrc
  source ~/.zshrc

• For Bash:

  echo 'export NODE_OPTIONS="--max_old_space_size=4096"' >> ~/.bashrc
  source ~/.bashrc

You can verify the new limit with:

node -e "console.log((require('v8').getHeapStatistics().heap_size_limit / 1024 / 1024).toFixed(2) + ' MB')"

Expected output:

~4144.00 MB

Increasing Heap Size on Windows (PowerShell or CMD)

Temporary (Current Session Only)

PowerShell:

$env:NODE_OPTIONS="--max_old_space_size=4096"
npx expo start

Command Prompt:

set NODE_OPTIONS=--max_old_space_size=4096
expo start

Permanent (System Environment Variable)

1. Press Win + R, type sysdm.cpl, press Enter.

2. Go to the Advanced tab -> click Environment Variables.

3. Under User Variables, click New:

   • Variable name: NODE_OPTIONS
   • Variable value: --max_old_space_size=4096

4. Click OK, restart your terminal.

Verify with:

node -e "console.log((require('v8').getHeapStatistics().heap_size_limit / 1024 / 1024).toFixed(2) + ' MB')"

Optional: package.json Shortcut

To avoid manually setting environment variables, add a start script:

For Windows (CMD-style)

"scripts": {
  "start": "set NODE_OPTIONS=--max_old_space_size=4096 && expo start"
}

Cross-platform (with cross-env)

Install the tool:

npm install --save-dev cross-env

Then in package.json:

"scripts": {
  "start": "cross-env NODE_OPTIONS=--max_old_space_size=4096 expo start"
}

Conclusion

Once I increased the heap size, Expo bundling no longer crashed, and the Jest worker errors disappeared. This is a common issue for heavier Expo React Native apps, and adjusting the memory limit is an effective fix.

If you're hitting bundling crashes or random process kills during development, check your heap size, it might be the culprit.

-- Mohammad