Fix: Claude Code 'API Key Not Found' Error — Complete Troubleshooting Guide

The Problem

You install Claude Code, run your first command, and get:

Error: API Key Not Found

Or variations like:

Claude API Error: 401 Unauthorized — No API key provided
Error: ANTHROPIC_API_KEY is not set

This is the #1 stumbling block for new Claude Code users. The fix is straightforward — you just need to get your API key into the right place. Let's walk through every possible cause and solution.

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Step 1: Get Your API Key (If You Haven't Already)

First, make sure you actually have an API key:

1. Go to the Anthropic Console 2. Log in (or create an account — you'll need to add billing) 3. Navigate to API Keys → Create Key 4. Copy the key (you'll only see it once — save it somewhere safe) 5. Top up your account with at least \$5 credit

> 💡 Tip: The API key starts with sk-ant-.... If yours doesn't look like that, you might have the wrong key.

External Links: - Anthropic Console — API Keys - Anthropic API Pricing - Anthropic API Documentation

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Step 2: Set the Environment Variable (The Standard Way)

Claude Code looks for your API key in the ANTHROPIC_API_KEY environment variable.

Method A: Export in Your Shell Profile (Recommended)

For Linux/macOS — add to your terminal profile (~/.zshrc, ~/.bashrc, or ~/.zprofile):

export ANTHROPIC_API_KEY="sk-ant-your-key-here"

Then reload:

source ~/.zshrc

For Windows (PowerShell) — add to your PowerShell profile:

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

Or add this to your $PROFILE:

$env:ANTHROPIC_API_KEY = "sk-ant-your-key-here"

Method B: Export Per-Session (Quick Test)

export ANTHROPIC_API_KEY="sk-ant-your-key-here"
claude

This only works for the current terminal session — close the terminal and it's gone.

Method C: .env File (For Project-Specific Setup)

Create a .env file in your project root:

ANTHROPIC_API_KEY=sk-ant-your-key-here

Then source it before running Claude Code:

export $(grep -v '^#' .env | xargs) && claude

> ⚠️ Important: Never commit your .env file to git! Add .env to .gitignore — and never use .env.example as your actual config file. If you accidentally expose your key, rotate it immediately.

External Links: - Dotenv (npm package) — auto-load .env files in Node.js projects - GitHub — .env.gitignore template

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Step 3: Verify It Worked

# Check that the env var is set
echo $ANTHROPIC_API_KEY
# Expected output: sk-ant-xxxxxxxxxxxxx
# Run Claude Code to confirm
claude --print "Hello, can you hear me?"

If Claude responds, you're all set.

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Step 4: If It Still Doesn't Work — Advanced Debugging

Problem: The Variable Shows Empty After Export

Possible cause: You exported it in the wrong shell profile, or the profile didn't source.

# Check your active shell
echo $SHELL  # Is it /bin/zsh or /bin/bash?

Fix: Edit the correct profile file — ~/.zshrc for Zsh, ~/.bashrc for Bash, ~/.bash_profile for login shells.

Problem: "Claude: command not found"

You haven't installed Claude Code yet:

npm install -g @anthropic-ai/claude-code

Or with the standalone installer:

curl -fsSL https://claude.ai/install | bash

External Links: - Claude Code Installation Guide - Claude Code GitHub Repository

Problem: "403 Forbidden" or "Billing required"

Your API key exists but either: - Your account has no billing set up — add credit - You're on a free trial that expired - The key was revoked — generate a new one

Problem: Multiple Terminal Windows / IDE Terminal

Environment variables are session-scoped. If you open a new terminal tab or an IDE's built-in terminal, that session won't have the variable. You need to source it in every new terminal, or use a global method (like your shell profile).

Problem: Using Zsh with Oh My Zsh

Oh My Zsh users should add the export to ~/.zshrc — not .zprofile or .bash_profile. The .zshrc file is sourced for every interactive Zsh session.

Problem: VS Code Terminal Doesn't Pick It Up

VS Code terminals might not source your shell profile. Two fixes:

1. Set it in VS Code settings: Add to .vscode/settings.json:

{
  "terminal.integrated.env.linux": {
    "ANTHROPIC_API_KEY": "sk-ant-your-key-here"
  }
}

2. Or add this to your VS Code settings.json (File → Preferences → Settings → Open Settings JSON):

"terminal.integrated.env.linux": {
  "ANTHROPIC_API_KEY": "sk-ant-your-key-here"
}

External Links: - VS Code Integrated Terminal Configuration - Oh My Zsh Documentation

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Verification Checklist

Use this checklist to confirm everything is working:

| Check | Command | Expected | |-------|---------|----------| | Key exists | echo $ANTHROPIC_API_KEY | sk-ant-... | | Claude Code installed | claude --version | A version number | | API reachable | claude --print "ping" | A response | | Works in VS Code | Open VS Code terminal, repeat above | Same results |

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Summary

The "API Key Not Found" error has three causes 99% of the time:

1. You don't have an API key yet → Get one at console.anthropic.com 2. You have a key but haven't set the env var → Add export ANTHROPIC_API_KEY=... to your shell profile 3. You set it but in the wrong session → Source your profile, restart terminal, or use a global setting

If none of the above works, check Anthropic's status page for any ongoing incidents, and consider asking on the Anthropic Discord or browsing GitHub Issues.

Related Articles: - How to Install Claude Code in 5 Minutes — full installation walkthrough - Effective Claude Code Prompts — get better results after you're set up - Claude Code vs GitHub Copilot — compare the tools