> For the complete documentation index, see [llms.txt](https://sub2.gitbook.io/sub2/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sub2.gitbook.io/sub2/popup-integration.md).

# Popup integration

Sub2 offers easy checkout integration with a popup window. It works by opening a URL starting with `www.sub2protocol.com/popup` followed by URL arguments. This makes it possible to create a custom button or other HTML elements on your website while still preserving all functionality in a separate window. The list of arguments can be seen here:

| Parameter              | Details                                                                                                                             |
| ---------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
| `recipient`            | Address of the recipient of the subscription payments.                                                                              |
| `cooldown`             | Number of seconds between payments. For example, 30 days is `cooldown=2592000`.                                                     |
| `token`                | Address of ERC-20 token that is paid with.                                                                                          |
| `amount`               | Amount of tokens paid each time. This is the actual decimal number e.g. `amount=10.5` and not the EVM integer version.              |
| `processing_fee_token` | Address of the ERC-20 token used for processing fee.                                                                                |
| `max_processing_fee`   | Amount of maximum processing fee. This is the actual decimal number e.g. `max_processing_fee=0.02` and not the EVM integer version. |
| `auction_duration`     | Duration of the auction period in seconds. This has to be less than or equal to `cooldown`.                                         |
| `initial_delay`        | Delay in seconds before the first payment is due.                                                                                   |
| `initial_payments`     | Number of initial payments with the creation of the subscription. If `initial_delay > 0` then no initial payments are made.         |
| `sponsor`              | Address of sponsor of the subscription.                                                                                             |
| `sponsor_signature`    | EIP-712 signature of sponsor permit. The permit has to contain the same parameters as given in the URL.                             |
| `permit_nonce`         | Nonce of the sponsor permit used for the signature.                                                                                 |
| `permit_deadline`      | UNIX time in seconds for when the provided sponsor signature will expire.                                                           |

The parameters `sponsor`, `sponsor_signature`, `permit_nonce` and `permit_deadline` should only be provided if there is an intention to sponsor the processing fee of the subscription. However, if there is an intention of making a sponsorship, *all* of these parameters should be provided.

{% hint style="info" %}
Note that there is no field for sender/subscriber. This is because the user should be able to chose which account they want to pay the subscription with.
{% endhint %}