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

# Create an exchange session for an external party

> Create an exchange session for an external party.

# Create an exchange session for an external party

To initiate Instant Account Verification for an external party using Dwolla's trusted open banking partners, you'll need to create an exchange session. Currently, Plaid and MX are the supported partners.

When creating an exchange session, provide the following information:

* `_links.exchange-partner`: The unique identifier for the desired open banking partner. Use the [list exchange partners](/docs/connect/api-reference/exchanges/list-exchange-partners) endpoint to retrieve available partners and their corresponding identifiers.
* `_links.redirect-url` (conditional): A **required** redirect URL for Plaid mobile/native app integrations. This URL will be used to redirect the user back to your application after completing the authorization process. For Plaid web-based integrations and MX exchange sessions, this parameter is **not required**.

### HTTP request

> `POST https://api.dwolla.com/external-parties/{id}/exchange-sessions`

### Request parameters

| Property | Required | Type   | Description                                                                                                                                      |
| -------- | -------- | ------ | ------------------------------------------------------------------------------------------------------------------------------------------------ |
| \_links  | yes      | object | A HAL-JSON link that represents the Exchange Partner resource. This identifies the open banking provider used for creating the exchange session. |

### HTTP status and error codes

| HTTP Status | Code         | Message                                                                                  | Description                                                                                                                                                                                   |
| ----------- | ------------ | ---------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 201         | -            | -                                                                                        | The Dwolla API accepted the request and created an exchange session resource. You can reference the Location header to retrieve a link that represents the created exchange session resource. |
| 400         | Invalid      | /\_links/exchange-partner/href is invalid.                                               | ValidationError. Returned if the exchange partner URL is invalid.                                                                                                                             |
| 400         | Invalid      | /\_links/redirect-url/href is invalid.                                                   | ValidationError. Returned if the redirect URL is invalid.                                                                                                                                     |
| 400         | Invalid      | The provided redirect URL must exactly match one of the configured URLs for the account. | ValidationError. The redirect url does not match what is configured for the Dwolla account.                                                                                                   |
| 401         | InvalidScope | Missing or invalid scopes for requested endpoint.                                        |                                                                                                                                                                                               |
| 403         | Forbidden    | The exchange partner specified does not support this product.                            | Returned if the exchange partner specified does not support the creation of exchange sessions.                                                                                                |
| 404         | NotFound     | The requested resource was not found.                                                    |                                                                                                                                                                                               |

### Request and Response

```bash theme={"dark"}
POST https://api.dwolla.com/external-parties/74a207b2-b7b7-4efa-8bf8-582148e7b980/exchange-sessions
Accept: application/vnd.dwolla.v1.hal+json
Content-Type: application/vnd.dwolla.v1.hal+json
Authorization: Bearer pBA9fVDBEyYZCEsLf/wKehyh1RTpzjUj5KzIRfDi0wKTii7DqY

{
    "_links": {
        "exchange-partner": {
            "href": "https://api.dwolla.com/exchange-partners/292317ec-e252-47d8-93c3-2d128e037aa4"
        },
        "redirect-url": {
            "href": "https://www.yourdomain.com/iav-callback"
        }
    }
}

HTTP/1.1 201 Created
Location: https://api.dwolla.com/exchange-sessions/fcd15e5f-8d13-4570-a9b7-7fb49e55941d
```

```php theme={"dark"}
/**
 * No example for this language yet.
 **/
```

```ruby theme={"dark"}
# Using dwolla_v2 - https://github.com/Dwolla/dwolla-v2-ruby
external_party_url = 'https://api.dwolla.com/external-parties/74a207b2-b7b7-4efa-8bf8-582148e7b980'
request_body = {
  _links: {
    'exchange-partner': {
      href: "https://api.dwolla.com/exchange-partners/292317ec-e252-47d8-93c3-2d128e037aa4"
    },
    'redirect-url': {
      href: "https://www.yourdomain.com/iav-callback"
    }
  }
}

exchange = app_token.post "#{external_party_url}/exchange-sessions", request_body
exchange.response_headers[:location] # => "https://api.dwolla.com/exchange-sessions/fcd15e5f-8d13-4570-a9b7-7fb49e55941d"
```

```python theme={"dark"}
# Using dwollav2 - https://github.com/Dwolla/dwolla-v2-python
external_party_url = 'https://api.dwolla.com/external-parties/74a207b2-b7b7-4efa-8bf8-582148e7b980'
request_body = {
  '_links': {
    'exchange-partner': {
      'href': 'https://api.dwolla.com/exchange-partners/292317ec-e252-47d8-93c3-2d128e037aa4'
    },
    'redirect-url': {
      'href': 'https://www.yourdomain.com/iav-callback'
    }
  }
}

exchange = app_token.post('%s/exchange-sessions' % external_party_url, request_body)
exchange.headers['location'] # => 'https://api.dwolla.com/exchange-sessions/fcd15e5f-8d13-4570-a9b7-7fb49e55941d'
```

```javascript theme={"dark"}
// Using dwolla-v2 - https://github.com/Dwolla/dwolla-v2-node
var externalPartyUrl =
  "https://api.dwolla.com/external-parties/74a207b2-b7b7-4efa-8bf8-582148e7b980";
var requestBody = {
  _links: {
    "exchange-partner": {
      href: "https://api.dwolla.com/exchange-partners/292317ec-e252-47d8-93c3-2d128e037aa4",
    },
    "redirect-url": {
      href: "https://www.yourdomain.com/iav-callback",
    },
  },
};

dwolla
  .post(`${externalPartyUrl}/exchange-sessions`, requestBody)
  .then((res) => res.headers.get("location")); // => 'https://api.dwolla.com/exchange-sessions/fcd15e5f-8d13-4570-a9b7-7fb49e55941d'
```