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Fix: Claude Code ANTHROPIC_API_KEY Not Set Error

How to fix the ANTHROPIC_API_KEY environment variable not set error in Claude Code.

claude-code troubleshooting setup

You just installed Claude Code, ran claude in your terminal, and got this error:

Error: ANTHROPIC_API_KEY environment variable is not set

This is the most common first-time setup issue. Here’s how to fix it.

Why This Happens

Claude Code needs an API key to authenticate with Anthropic’s servers. Without it, the CLI cannot make any requests. The error means either:

  1. You haven’t set the environment variable yet
  2. You set it in a different terminal session
  3. Your shell configuration isn’t loading properly

Solution

Step 1: Get Your API Key

  1. Go to console.anthropic.com
  2. Sign in or create an account
  3. Navigate to API Keys section
  4. Create a new key and copy it

Step 2: Set the Environment Variable

For macOS/Linux (zsh):

echo 'export ANTHROPIC_API_KEY="your-key-here"' >> ~/.zshrc
source ~/.zshrc

For macOS/Linux (bash):

echo 'export ANTHROPIC_API_KEY="your-key-here"' >> ~/.bashrc
source ~/.bashrc

For Windows (PowerShell):

[System.Environment]::SetEnvironmentVariable('ANTHROPIC_API_KEY', 'your-key-here', 'User')

Then restart your terminal.

Step 3: Verify

echo $ANTHROPIC_API_KEY

You should see your key (or at least the first few characters). Now run claude again.

Common Mistakes

Wrong shell config file

Check which shell you’re using:

echo $SHELL
  • /bin/zsh → use .zshrc
  • /bin/bash → use .bashrc

Typo in variable name

It must be exactly ANTHROPIC_API_KEY. Not ANTHROPIC_KEY, not CLAUDE_API_KEY.

Forgot to source

After editing your shell config, either:

  • Run source ~/.zshrc (or .bashrc)
  • Or open a new terminal window

Key has extra spaces

Make sure there are no spaces around the equals sign or inside the quotes:

# Wrong
export ANTHROPIC_API_KEY = "sk-..."
export ANTHROPIC_API_KEY="sk-... "

# Correct
export ANTHROPIC_API_KEY="sk-..."

Using a .env File (Alternative)

If you prefer not to set a global environment variable, you can use a .env file in your project:

# .env
ANTHROPIC_API_KEY=your-key-here

Then run Claude Code with:

source .env && claude

Or use a tool like direnv to auto-load it.

Security Note

Never commit your API key to git. Add .env to your .gitignore:

echo ".env" >> .gitignore

If you accidentally exposed your key, revoke it immediately in the Anthropic console and create a new one.

Still Not Working?

If the error persists after following these steps:

  1. Open a completely new terminal window
  2. Check if the variable is set: printenv | grep ANTHROPIC
  3. Try setting it inline: ANTHROPIC_API_KEY="your-key" claude

If inline works but the export doesn’t, your shell config file isn’t being loaded. Check if you have a .zprofile or .bash_profile that might be conflicting.