Fix: Next.js Build Out of Heap Memory Error During Deployment

You're deploying your Next.js application. The build starts fine, static pages generate successfully, and then—crash. FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory. You increase Node's memory allocation to 8GB, try again, same result. Sound familiar?

This Next.js build out of memory error is particularly frustrating because the usual fix—throwing more RAM at the problem—doesn't work. The real culprit is often hiding in plain sight: large files accidentally committed to your repository that get bundled into the build context.

In this article, we'll diagnose why this happens, trace it to a common root cause involving service account files, and implement a proper fix that keeps your builds lightweight and your secrets secure.

The Problem — The Build Process Crashes with an 'Out of Heap Memory' Error in CI/CD Environments

Let's look at a typical scenario. You're building a Next.js 15 application—perhaps for a restaurant loyalty program, an e-commerce platform, or any project that connects to external services. Locally, everything seems fine during development. But when you run next build or deploy to Vercel, you get hit with this:

✓ Compiled successfully
✓ Collecting page data
✓ Generating static pages (18/18)
FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
 
 1: 0x100a3d0f8 node::Abort() [node]
 2: 0x100a3d278 node::OOMErrorHandler(char const*, v8::OOMDetails const&) [node]
 3: 0x100bc1990 v8::internal::V8::FatalProcessOutOfMemory(...)

The build completes the compilation phase without issues. It even generates your static pages successfully. Then, during the final bundling or optimization phase, memory consumption spikes uncontrollably until Node.js crashes.

You try the standard remediation:

# ❌ Doesn't help with this particular issue
NODE_OPTIONS="--max-old-space-size=8192" npm run build

Even allocating 8GB of heap memory doesn't solve it. The build still fails. This indicates the problem isn't about the memory limit being too low—it's about something in your project causing unbounded memory consumption.

This issue was reported in GitHub Issue #76704, where a developer experienced the exact same pattern: a "not really large app" that inexplicably consumed all available memory during builds. The breakthrough came when they discovered large service account files hidden in their repository.

Why This Happens — Inclusion of Large Service Account Files or Heavy Dependencies in the Repository Bundle

Here's what's actually happening. During the Next.js build process, the bundler (whether Webpack or Turbopack) analyzes your project's dependency graph. It traces imports, resolves modules, and processes files to create optimized bundles. When certain files end up in the build context—either through direct imports or because they're present in directories the bundler scans—they get loaded into memory.

The Service Account File Trap

Service account files are a particularly insidious offender. Consider this common pattern for Firebase or Google Cloud integration:

// ❌ Broken: Importing a local JSON file directly
import serviceAccount from "./firebase-service-account.json";
import admin from "firebase-admin";
 
admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
});
 
export const db = admin.firestore();

This looks innocent enough. But here's the problem:

1. Service account files can be large. While a typical service account JSON is only a few KB, some projects accumulate multiple service account files, backup copies, or files with embedded certificates that balloon in size.

2. They may contain or reference other large files. In some configurations, service account directories include large key files, certificate chains, or bundled dependencies.

3. They get processed during static analysis. Even if you only import a single field from the JSON, the entire file (and anything it references) gets loaded into the bundler's memory.

4. Multiple copies multiply the problem. If you have firebase-admin-sdk.json, firebase-admin-sdk-backup.json, and firebase-admin-sdk-prod.json all in your repo, and any of them get pulled into the build context, you're tripling your memory overhead.

The Hidden Dependencies Problem

Beyond service account files, similar issues arise from:

• Large JSON data files committed for testing or seeding
• Binary files accidentally tracked by Git (images, PDFs, compiled assets)
• Node modules copied into the source tree instead of being installed via package.json
• Backup files (.bak, .old) that duplicate large dependencies

The bundler doesn't discriminate. If a file is in a directory it scans, and it's importable, it becomes part of the build context.

Why More Memory Doesn't Help

When the bundler encounters a large file or a file that triggers extensive processing, it doesn't just load the file once. It may:

• Parse and transform the content multiple times
• Create multiple in-memory representations for different optimization passes
• Hold references that prevent garbage collection

This explains why increasing --max-old-space-size doesn't help. You're not dealing with a "needs more memory" problem—you're dealing with a "shouldn't be processing this at all" problem.

The Solution — Removing Sensitive Service Accounts from the Repo and Using Environment Variables Instead

The fix has two parts: remove the problematic files from your repository, and restructure your code to load credentials from environment variables instead.

Step 1: Identify the Culprits

First, find large files in your repository:

# Find files larger than 100KB in your project
find . -type f -size +100k -not -path "./node_modules/*" -not -path "./.git/*"
 
# Check for common service account patterns
find . -name "*service-account*" -o -name "*credentials*" -o -name "*firebase-admin*"

Look for JSON files containing private keys, certificate files, or any unexpectedly large files in your source directories.

Step 2: Remove and Add to .gitignore

Once identified, remove these files from Git tracking:

# Remove from Git but keep local copy (you'll need the values for env vars)
git rm --cached firebase-service-account.json
git rm --cached google-credentials.json
 
# Commit the removal
git commit -m "Remove service account files from repository"

Add them to .gitignore to prevent future commits:

# .gitignore
 
# Service account and credential files
**/firebase-service-account*.json
**/google-credentials*.json
**/service-account*.json
**/*-credentials.json
*.pem
*.key
 
# Environment files (should already be here)
.env
.env.local
.env.*.local

Step 3: Refactor to Use Environment Variables

Now, restructure your code to load credentials from environment variables:

// ✅ Fixed: Loading credentials from environment variables
import admin from "firebase-admin";
 
// Parse the service account from an environment variable
const serviceAccount = JSON.parse(
  process.env.FIREBASE_SERVICE_ACCOUNT_KEY || "{}"
);
 
if (!admin.apps.length) {
  admin.initializeApp({
    credential: admin.credential.cert(serviceAccount),
  });
}
 
export const db = admin.firestore();

Set the environment variable in your deployment platform. For Vercel:

# In your Vercel project settings, add:
# Name: FIREBASE_SERVICE_ACCOUNT_KEY
# Value: (paste the entire JSON content, minified)

For local development, use .env.local:

# .env.local (DO NOT commit this file)
FIREBASE_SERVICE_ACCOUNT_KEY='{"type":"service_account","project_id":"your-project",...}'

Step 4: Handle Multi-Line JSON Gracefully

Service account JSON files are multi-line, which can cause issues with some environment variable parsers. Here's a more robust approach:

// ✅ Fixed: Robust credential loading with error handling
import admin from "firebase-admin";
 
function getFirebaseAdmin() {
  if (admin.apps.length) {
    return admin;
  }
 
  const serviceAccountKey = process.env.FIREBASE_SERVICE_ACCOUNT_KEY;
 
  if (!serviceAccountKey) {
    throw new Error(
      "FIREBASE_SERVICE_ACCOUNT_KEY environment variable is not set"
    );
  }
 
  try {
    // Handle both stringified JSON and base64-encoded values
    let credentials;
 
    if (serviceAccountKey.startsWith("{")) {
      credentials = JSON.parse(serviceAccountKey);
    } else {
      // Assume base64 encoded
      const decoded = Buffer.from(serviceAccountKey, "base64").toString(
        "utf-8"
      );
      credentials = JSON.parse(decoded);
    }
 
    admin.initializeApp({
      credential: admin.credential.cert(credentials),
    });
 
    return admin;
  } catch (error) {
    throw new Error(`Failed to parse Firebase credentials: ${error.message}`);
  }
}
 
export const db = getFirebaseAdmin().firestore();

To use base64 encoding (recommended for complex JSON):

# Encode your service account file
cat firebase-service-account.json | base64
 
# Add the output as FIREBASE_SERVICE_ACCOUNT_KEY in your deployment platform

Prevention & Best Practices — Proper Use of .gitignore and Secret Management to Keep the Build Context Lightweight

Fixing the immediate problem is essential, but preventing recurrence requires establishing proper practices for credential and large file management.

Establish a Comprehensive .gitignore

Start with a .gitignore that explicitly excludes credential patterns:

# Credentials and secrets
**/credentials/
**/secrets/
*.pem
*.key
*.p12
*.pfx
*-service-account*.json
*-credentials*.json
firebase-adminsdk*.json
google-cloud-key*.json
 
# Environment files
.env
.env.*
!.env.example
 
# Large data files
*.sql
*.sqlite
*.db
data/*.json
seed-data/
 
# Build artifacts that shouldn't be committed
.next/
out/
build/
dist/
 
# IDE and OS files
.DS_Store
*.swp
.idea/
.vscode/settings.json

Use Secret Management Services

For production deployments, consider dedicated secret management instead of environment variables:

Implement Pre-Commit Hooks

Use Git hooks to prevent accidental commits of sensitive files:

# Install husky for Git hooks
npm install --save-dev husky
 
# Initialize husky
npx husky init

Create a pre-commit hook:

#!/bin/sh
# .husky/pre-commit
 
# Check for potential credential files
if git diff --cached --name-only | grep -E "(service-account|credentials|\.pem|\.key)"; then
  echo "ERROR: Attempting to commit potential credential files!"
  echo "Remove these files from staging and add them to .gitignore"
  exit 1
fi

Audit Your Repository Regularly

Run periodic checks for large or sensitive files:

# Find large files in Git history
git rev-list --objects --all | \
  git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' | \
  sed -n 's/^blob //p' | \
  sort -rnk2 | \
  head -20
 
# Check for files that match sensitive patterns
git ls-files | grep -E "(credential|secret|service-account|\.pem|\.key)"

Keep Your Build Context Clean

Beyond credentials, maintain awareness of what enters your build:

1. Never import large static data at build time. Fetch it at runtime or use getStaticProps/getServerSideProps.
2. Exclude test fixtures from production builds using conditional exports in package.json.
3. Review your bundle size regularly with @next/bundle-analyzer.
4. Use dynamic imports for heavy optional dependencies.

// ✅ Better: Dynamic import for optional heavy dependencies
async function generatePDF(data) {
  const { default: PDFDocument } = await import("pdfkit");
  // Use PDFDocument...
}

Key Takeaways

• Next.js build out of memory errors often stem from large files in the build context, not insufficient RAM allocation.
• Service account files are a common culprit—they should never be committed to version control.
• Environment variables or secret managers are the correct approach for handling credentials in Next.js deployments.
• Comprehensive .gitignore patterns with pre-commit hooks prevent accidental inclusion of sensitive or large files.
• Regular repository audits help catch files that shouldn't be tracked before they cause build failures.

Next Steps

1. Audit your repository now. Run find . -type f -size +100k and check for service account or credential files.
2. Update your .gitignore with the patterns from this article before your next commit.
3. Migrate existing credentials to environment variables in your deployment platform.
4. Set up pre-commit hooks using Husky to prevent future accidents.
5. Review the original GitHub issue for additional context and community solutions.

If your builds are still failing after removing large files, investigate dynamic imports, bundle splitting, or consider using standalone output mode for more controlled production builds. The goal is always the same: keep your build context as lightweight as possible.