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

# Legacy API Authentication

> Send your Formcarry API key in the api_key header to authenticate legacy API requests against formcarry.com/api.

<Warning>
  This page covers authentication for the **legacy** Formcarry API. For new integrations, see [v1 Authentication](/docs/api/authentication).
</Warning>

The legacy API authenticates every request with an API key sent in the `api_key` header.

## Get your API key

1. Open your Formcarry dashboard.
2. Go to **Settings** → **API Keys**.
3. Copy your key.

## Send the key

Add the `api_key` header to every request:

```bash theme={null}
curl https://formcarry.com/api/form/FORM_ID/submissions \
  -H "api_key: YOUR_API_KEY"
```

<Warning>
  Treat API keys like passwords. Do not commit them to source control or expose them in client-side code.
</Warning>

## Errors

* `401 Unauthorized` — the `api_key` header is missing or the key is invalid.
* `403 Forbidden` — the key does not have access to the requested form.


## Related topics

- [Legacy Formcarry API Overview](/docs/api/legacy/overview.md)
- [Legacy Forms API — Create and Delete Forms](/docs/api/legacy/forms.md)
- [API Authentication with Bearer Tokens](/docs/api/authentication.md)
- [Legacy Submissions API — List and Filter Submissions](/docs/api/legacy/submissions.md)
- [Formcarry API Overview](/docs/api/overview.md)