npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules'
npm ERR! Error: EACCES: permission denied, mkdir '/usr/local/lib/node_modules/some-package'

npm is trying to write to a system directory that your user doesn’t own. This happens when you install Node.js via the system package manager and then try npm install -g.

Do NOT fix this with sudo npm install -g. That creates files owned by root and causes more permission problems later.

Fix 1: Use nvm (Best Solution)

nvm (Node Version Manager) installs Node in your home directory, so you never need sudo.

# Install nvm
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.0/install.sh | bash

# Restart your terminal, then:
nvm install --lts
nvm use --lts

# Verify
which node    # should show ~/.nvm/...
which npm     # should show ~/.nvm/...

# Now global installs work without sudo
npm install -g typescript

If you already have Node installed via Homebrew or apt, uninstall it first:

# Mac
brew uninstall node

# Ubuntu/Debian
sudo apt remove nodejs

Fix 2: Change npm’s Default Directory

If you don’t want nvm, tell npm to use a directory you own:

# Create a directory for global packages
mkdir -p ~/.npm-global

# Configure npm to use it
npm config set prefix '~/.npm-global'

# Add to your PATH (add to ~/.bashrc or ~/.zshrc)
export PATH=~/.npm-global/bin:$PATH

# Reload shell
source ~/.bashrc  # or source ~/.zshrc

# Now global installs work
npm install -g typescript

Fix 3: Fix Ownership (Quick Fix)

If you just want it to work right now:

# Take ownership of the npm directories
sudo chown -R $(whoami) /usr/local/lib/node_modules
sudo chown -R $(whoami) /usr/local/bin
sudo chown -R $(whoami) /usr/local/share

This works but isn’t ideal — system updates might reset the permissions.

Why NOT to Use sudo

# ❌ Never do this
sudo npm install -g some-package

Problems with sudo:

• Creates files owned by root in your project
• Future npm install commands may fail with permission errors
• Security risk — you’re running untrusted package scripts as root
• Breaks when you try to update or uninstall later

Prevention

The best approach: install Node via nvm from the start. Add this to your setup checklist for new machines:

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.0/install.sh | bash
nvm install --lts

You’ll never see EACCES again.