Authentication

Secure your Claude API integration with proper authentication

title: Authentication description: Secure your Claude API integration with proper authentication

Learn how to authenticate with the Claude API, manage API keys securely, and implement best practices for production applications.

API Keys

Getting Your API Key

1. Go to console.anthropic.com↗
2. Navigate to API Keys
3. Click Create Key
4. Copy and securely store the key

Important: API keys are only shown once. Store them securely immediately after creation.

Key Format

API keys follow this format:

• Prefix: sk-ant- (indicates Anthropic key)
• Type: api03 (current key version)
• Secret: Unique identifier

Authentication Methods

Header Authentication (Recommended)

Include the API key in the x-api-key header:

SDK Authentication

SDKs handle authentication automatically from environment variables:

Python:

TypeScript:

Environment Variables

Setting Up

Linux/macOS (bash/zsh):

Windows (PowerShell):

Docker:

Or pass at runtime:

Using .env Files

For local development, use .env files:

With Node.js:

With Python:

Never commit .env files! Add .env to your .gitignore.

Security Best Practices

1. Never Expose Keys in Code

❌ Wrong:

✅ Correct:

2. Use Secrets Management

For production, use proper secrets management:

AWS Secrets Manager:

HashiCorp Vault:

3. Rotate Keys Regularly

• Create a new key before revoking the old one
• Update all applications using the key
• Revoke the old key only after confirming the new one works
• Set up alerts for key usage anomalies

4. Use Separate Keys for Environments

| Environment | Key Purpose | |-------------|-------------| | Development | Individual developer testing | | Staging | Integration testing | | Production | Live application |

5. Implement Key Scoping

If your app has multiple services, use different keys:

Server-Side Integration

Proxy Pattern

Never expose API keys to the client. Use a server-side proxy:

Rate Limiting Your Proxy

Protect your API key with rate limiting:

Troubleshooting

Invalid API Key

Error:

Solutions:

1. Verify the key is correct (no extra spaces)
2. Check the key hasn't been revoked
3. Ensure environment variable is set correctly:
   Bash

Missing API Key

Error:

Solutions:

1. Check header name is x-api-key (lowercase)
2. Verify environment variable name matches SDK expectations
3. Ensure .env file is being loaded

Permission Denied

Error:

Solutions:

1. Check your API key's permissions in the console
2. Verify you're on the correct pricing tier
3. Contact support if permissions should be available

Key Management Checklist

• [ ] API key stored in environment variable
• [ ] .env files added to .gitignore
• [ ] Production keys in secrets manager
• [ ] Separate keys for each environment
• [ ] Key rotation schedule established
• [ ] Usage monitoring enabled
• [ ] Alerts configured for anomalies

Next Steps

• Learn about the Messages API →
• Implement tool use →
• Configure Claude Code →