> ## Documentation Index
> Fetch the complete documentation index at: https://docs.datalinkapis.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

> How to authenticate requests to the DataLink APIs platform.

## Bearer token

All requests to the DataLink APIs platform must include your API key as a Bearer token in the `Authorization` header.

```bash theme={null}
Authorization: Bearer dl_live_YOUR_KEY
```

## Example

```bash theme={null}
curl -X POST https://api.datalinkapis.com/v1/email \
  -H "Authorization: Bearer dl_live_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "email": "test@example.com" }'
```

## Getting your API key

1. Log in to your [DataLink dashboard](https://datalinkapis.com/dashboard)
2. Navigate to **API Keys**
3. Copy your key — it is shown once in full at creation

## Key format

| Prefix     | Environment                                           |
| ---------- | ----------------------------------------------------- |
| `dl_live_` | Production — real credits are deducted                |
| `dl_test_` | Test mode — no credits deducted, responses are mocked |

<Note>
  Test mode keys are available on Starter and Pro plans.
</Note>

## Security best practices

<AccordionGroup>
  <Accordion title="Never expose keys client-side">
    API keys must only be used server-side. Embedding a key in browser JavaScript, a mobile app binary, or a public repository will expose it to anyone who reads the source.
  </Accordion>

  <Accordion title="Use environment variables">
    Store your key in an environment variable (e.g. `DATALINK_API_KEY`) and reference it in code — never hardcode it as a string literal.
  </Accordion>

  <Accordion title="Rotate keys if compromised">
    If you suspect a key has been exposed, generate a new one from the dashboard immediately. Old keys are revoked as soon as a replacement is created.
  </Accordion>
</AccordionGroup>

## Error responses

If your key is missing or invalid, the API returns a `401` response:

```json theme={null}
{
  "error": "Unauthorized",
  "message": "Invalid or missing API key."
}
```

If your key is valid but your account has no remaining credits, you will receive a `402`:

```json theme={null}
{
  "error": "Payment Required",
  "message": "Insufficient credits. Top up your account or upgrade your plan."
}
```