| Paddle account type | Paddle Billing | Paddle Billing or Paddle Classic (legacy). |
| Sandbox (Use the Paddle sandbox) | On | Uses the sandbox credentials and test cards. Turn it off to take real payments. |
| Live / Sandbox API key (Billing) | None | From Developer Tools → Authentication → API keys. |
| Live / Sandbox client-side token (Billing) | None | Starts with live_ or test_. With the wrong prefix, Paddle stays hidden at checkout. |
| Live / Sandbox webhook secret (Billing) | None | Filled in automatically by Set up webhook, or paste the secret key of a destination you created yourself. |
| Live / Sandbox Vendor ID (Classic) | None | From Developer Tools → Authentication. |
| Live / Sandbox API Auth Code (Classic) | None | From Developer Tools → Authentication. |
| Live / Sandbox Public Key (Classic) | None | From Developer Tools → Public Key, including the BEGIN/END lines. Payments are only marked paid when Paddle’s signature verifies against it. |
| Webhooks | None | Your webhook URL; for Billing also the Set up webhook button. |