The npm ci sync error occurs when package.json and package-lock.json have mismatched dependencies. Run npm install locally to regenerate the lockfile, then commit the changes.
npm ci (clean install) is designed for automated environments and requires strict synchronization between package.json and package-lock.json. Unlike `npm install`, which updates the lockfile when mismatches are found, `npm ci` fails immediately if there's any discrepancy. This error typically occurs when someone edited package.json without running npm install afterward, or when team members use different npm versions that generate incompatible lockfiles.
Run npm install locally to sync the files:
# Delete lockfile and reinstall
rm package-lock.json
npm install
# Commit the new lockfile
git add package-lock.json
git commit -m "Regenerate package-lock.json"If you just need to sync the lockfile:
# Update lockfile only
npm install --package-lock-only
# Commit changes
git add package-lock.json
git commit -m "Sync package-lock.json"For a complete reset:
# Remove everything
rm -rf node_modules package-lock.json
# Clear cache
npm cache clean --force
# Reinstall
npm install
# Verify npm ci works
npm ciIf using flags like --legacy-peer-deps, add to .npmrc:
# Create .npmrc in project root
echo "legacy-peer-deps=true" >> .npmrc
# Commit .npmrc
git add .npmrc
git commit -m "Add npm configuration"This ensures CI uses the same settings as local development.
Ensure same versions everywhere:
# Create .nvmrc
node -v > .nvmrc
# Add engines to package.json
{
"engines": {
"node": ">=18.0.0",
"npm": ">=9.0.0"
}
}Update CI configuration to use matching versions.
If npm ci keeps failing, use npm install as fallback:
# GitHub Actions example
- name: Install dependencies
run: npm install
# instead of: npm ciNote: This is less strict but more forgiving of mismatches.
npm ci was introduced specifically for CI/CD environments where reproducibility is critical. It:
1. Deletes node_modules before installing
2. Installs exact versions from package-lock.json
3. Never modifies package.json or package-lock.json
4. Fails fast if files are out of sync
The strict behavior is intentional—it prevents surprise package updates during deployments. The error is a feature, not a bug.
For Docker builds, run npm install inside the Docker container to ensure the lockfile matches the container's npm version, not your host machine's.
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