# Authentication

### Overview

The Nansen API uses API key authentication. All requests must include your API key in the `apikey` header.

### Getting Your API Key

1. Log in to your [Nansen Account](https://app.nansen.ai/auth/agent-setup)
2. Generate a new API key

### Using Your API Key

#### Header Format

```
apikey: YOUR_API_KEY
```

#### curl Example

```bash
curl -X POST 'https://api.nansen.ai/api/v1/smart-money/holdings' \
  -H 'Content-Type: application/json' \
  -H 'apikey: YOUR_API_KEY' \
  -d '{"chains": ["ethereum"]}'
```

#### Python Example

```python
import httpx

headers = {
    "Content-Type": "application/json",
    "apikey": "YOUR_API_KEY"
}

response = httpx.post(
    "https://api.nansen.ai/api/v1/smart-money/holdings",
    headers=headers,
    json={"chains": ["ethereum"]}
)
```

#### Python with Environment Variable

```python
import os
import httpx

API_KEY = os.environ.get("NANSEN_API_KEY")

headers = {
    "Content-Type": "application/json",
    "apikey": API_KEY
}

response = httpx.post(
    "https://api.nansen.ai/api/v1/smart-money/holdings",
    headers=headers,
    json={"chains": ["ethereum"]}
)
```

### Authentication Errors

#### 401 Unauthorized

Returned when the API key is missing or invalid:

```json
{
  "error": {
    "code": "UNAUTHORIZED",
    "message": "Invalid or missing API key"
  }
}
```

**Solutions:**

* Verify your API key is correct
* Ensure the header name is `apikey` (lowercase)
* Check that the key hasn't been revoked

#### 403 Forbidden

Returned when the API key doesn't have permission for the requested resource:

```json
{
  "error": {
    "code": "FORBIDDEN",
    "message": "Insufficient permissions for this endpoint"
  }
}
```

**Solutions:**

* Verify your subscription tier includes access to this endpoint
* Contact support to upgrade your plan

### Key Management

If your key is compromised:

1. Immediately revoke it in your dashboard
2. Generate a new key
3. Update all applications using the old key


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Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
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```

The question should be specific, self-contained, and written in natural language.
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Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.