FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory

Node.js ran out of memory. The default limit is ~1.5GB. Large builds, data processing, or memory leaks can hit this.

Fix 1: Increase Memory Limit

# Run with more memory (4GB)
node --max-old-space-size=4096 script.js

# For npm scripts
NODE_OPTIONS="--max-old-space-size=4096" npm run build

# Add to .bashrc/.zshrc for permanent fix
export NODE_OPTIONS="--max-old-space-size=4096"

Common values:

• 2048 = 2GB
• 4096 = 4GB
• 8192 = 8GB

Fix 2: Fix Your Build Tool

This often happens during builds with webpack, Vite, or Next.js.

Next.js:

// next.config.js — reduce memory usage
module.exports = {
  swcMinify: true,  // uses less memory than Terser
}

Webpack:

# Use the memory-efficient mode
NODE_OPTIONS="--max-old-space-size=4096" npx webpack --mode production

TypeScript:

# tsc can be memory-hungry on large projects
NODE_OPTIONS="--max-old-space-size=4096" npx tsc

Fix 3: Find the Memory Leak

If increasing memory just delays the crash, you have a leak.

// Check memory usage in your code
console.log(process.memoryUsage());
// {
//   rss: 50MB,        ← total memory
//   heapUsed: 30MB,   ← actual usage
//   heapTotal: 40MB   ← allocated heap
// }

Common leak causes:

• Growing arrays/objects that are never cleared
• Event listeners that are never removed
• Closures holding references to large objects
• Caching without size limits

Profile it:

# Generate a heap snapshot
node --inspect script.js
# Open chrome://inspect in Chrome, take heap snapshots

Fix 4: Process Data in Streams

If you’re loading large files into memory:

// ❌ Loads entire file into memory
const data = fs.readFileSync('huge-file.json', 'utf8');
const parsed = JSON.parse(data);

// ✅ Stream it
const stream = fs.createReadStream('huge-file.json');
stream.on('data', chunk => {
  // Process chunk by chunk
});

Fix 5: Docker / CI Environments

Containers often have less memory than your local machine.

# Dockerfile
ENV NODE_OPTIONS="--max-old-space-size=2048"

# GitHub Actions
env:
  NODE_OPTIONS: "--max-old-space-size=4096"

# Docker Compose — give the container more memory
services:
  app:
    mem_limit: 4g

Quick Fixes by Scenario

Scenario	Fix
npm run build crashes	NODE_OPTIONS="--max-old-space-size=4096" npm run build
tsc crashes	Same NODE_OPTIONS fix
Script processing large data	Use streams instead of loading all into memory
Docker build crashes	Add ENV NODE_OPTIONS to Dockerfile
Keeps crashing even with more memory	You have a memory leak — profile it