This is only applicable to Paddle Classic
For products, you can define the redirect behavior on the product create/edit page, under the “Set where the users go after checkout” section.
For subscriptions, the URL needs to be defined in the ‘success’ argument (see Success Redirect property in the Checkout Parameters documentation), when calling the Paddle.checkout.open() method in your Paddle.js implementation.
Equally, if using a static link, you can set it in the ‘data-success’ value in your link:
<a href="#!" class="paddle_button" data-product="12345" data-success="http://your-example-url.com">Buy Now!</a>