Claude API Environment Setup Guide

Set up your Anthropic API key securely. Store it in .env files, environment variables, and secrets managers. Avoid hardcoding keys in source code.

Keeping your Anthropic API key secure is critical — leaked keys result in unexpected charges.

Step 1: Get your API key

1. Go to console.anthropic.com
2. Create an account or sign in
3. Navigate to Settings → API Keys
4. Click Create Key — give it a descriptive name (e.g. "dev-local")
5. Copy the key immediately — it is shown only once

Step 2: Store in a .env file (local development)

# .env — add this to .gitignore
ANTHROPIC_API_KEY=sk-ant-api03-your-key-here

# Python — load with python-dotenv
pip install python-dotenv

from dotenv import load_dotenv
import anthropic

load_dotenv()  # reads .env into os.environ

client = anthropic.Anthropic()  # picks up ANTHROPIC_API_KEY automatically

Step 3: Add .env to .gitignore

# .gitignore
.env
.env.local
.env.*.local
*.key

Production: use a secrets manager

# AWS Secrets Manager example
import boto3
import json
import anthropic

def get_secret(secret_name: str) -> str:
    client = boto3.client("secretsmanager", region_name="us-east-1")
    response = client.get_secret_value(SecretId=secret_name)
    return json.loads(response["SecretString"])["ANTHROPIC_API_KEY"]

api_key = get_secret("prod/anthropic")
claude = anthropic.Anthropic(api_key=api_key)

Vercel / serverless deployment

# Set via Vercel CLI
vercel env add ANTHROPIC_API_KEY production

# Or in vercel.json (use env vars, not literal values)
# In your function:
import anthropic
client = anthropic.Anthropic()  # reads process.env.ANTHROPIC_API_KEY in Node.js

Check your key is working

import anthropic

client = anthropic.Anthropic()
try:
    # Cheapest possible call to verify auth
    r = client.messages.create(
        model="claude-haiku-4-5-20251001",
        max_tokens=10,
        messages=[{"role": "user", "content": "Hi"}]
    )
    print("Key valid. Model:", r.model)
except anthropic.AuthenticationError:
    print("Invalid API key — check ANTHROPIC_API_KEY in your environment")

For Python quickstart once your key is set, see the Python quickstart. For Node.js, see the Node.js quickstart.

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