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

# Reference

Complete reference for Offramp URL parameters and configuration options.

<Warning>
  **Security Requirements must be enforced**: Your backend API that generates session tokens must implement proper security measures. See [Security Requirements](/onramp/security-requirements) for complete implementation guidance.
</Warning>

## URL Format

```bash theme={null}
https://pay.coinbase.com/v3/sell/input?sessionToken=<token>&partnerUserRef=<id>&redirectUrl=<url>
```

## URL Parameters

The following table outlines parameters to generate the Offramp URL

| Parameter              | Req'd | Type    | Description                                                                                                                                                                                                                                                                                                       |
| :--------------------- | :---- | :------ | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `sessionToken`         | Yes   | String  | Token generated by the [Session Token API](#getting-a-session-token).                                                                                                                                                                                                                                             |
| `redirectUrl`          | Yes   | String  | URL to redirect the user to after they send crypto. Production URLs must be added to your domain allowlist (see [Security Requirements](/onramp/security-requirements)). Use [Offramp Transaction Status API](/onramp/offramp/transaction-status#sell-transaction-status) to fetch the send `to_address` details. |
| `partnerUserRef`       | Yes   | String  | Unique ID representing the end-user. Must be less than 50 chars. Use with the [Offramp Transaction Status API](/onramp/offramp/transaction-status#offramp-transaction-status) to retrieve transactions made during the session.                                                                                   |
| `defaultNetwork`       | No    | String  | Default network that should be selected when multiple networks are present                                                                                                                                                                                                                                        |
| `defaultAsset`         | No    | String  | Default asset that should be selected when multiple assets are present                                                                                                                                                                                                                                            |
| `presetCryptoAmount`   | No    | Number  | Preset crypto amount value                                                                                                                                                                                                                                                                                        |
| `presetFiatAmount`     | No    | Number  | Preset fiat amount value (for USD, CAD, GBP, EUR only). Ignored if `presetCryptoAmount` is also set.                                                                                                                                                                                                              |
| `defaultCashoutMethod` | No    | String  | Default payment method to cashout fiat ("FIAT\_WALLET", "CRYPTO\_ACCOUNT", "ACH\_BANK\_ACCOUNT", "PAYPAL")                                                                                                                                                                                                        |
| `fiatCurrency`         | No    | String  | e.g: USD, CAD, GBP, etc.                                                                                                                                                                                                                                                                                          |
| `disableEdit`          | No    | Boolean | If set to `true`, prevents users from editing their order in the One-Click Sell flow. By default, this is set to `false`.                                                                                                                                                                                         |

## Example

```bash theme={null}
https://pay.coinbase.com/v3/sell/input?sessionToken=abc123xyz&partnerUserRef=user-789&redirectUrl=https://yourapp.com
```

<Info>
  All transactions made during the session are linked to `partnerUserRef` which can be used with the [Transaction Status API](/onramp/offramp/transaction-status) to retrieve transactions later.
</Info>

## Creating Session Tokens

To get a `sessionToken`, call the [Session Token API](/api-reference/rest-api/onramp-offramp/create-session-token) from your backend:

```bash theme={null}
cdpcurl -X POST 'https://api.developer.coinbase.com/onramp/v1/token' \
  -k ~/Downloads/cdp_api_key.json \
  -d '{
    "addresses": [{
      "address": "0x1234567890abcdef1234567890abcdef12345678",
      "blockchains": ["base", "ethereum"]
    }],
    "clientIp": "192.0.2.1"
  }'
```

See the [Quickstart guide](/onramp/introduction/quickstart#try-offramp) for a complete example.