# Callbacks

Learn how to register a callback URL and security key for commercetools InStore.

### Register a callback URL and security key

1. Log in to the InStore Center.
2. On the left-hand navigation, click **Environment**.
3. Click the **Integration Settings** tab.
4. In the **Token Retrieval URL** field, enter your callback URL.
5. In the **Callback API Key** field, enter your API key. This key ensures secure communication.
6. Click **SAVE CHANGES**.

After the callback URL and security key are registered, the InStore application uses an HTTPS GET call to retrieve payment cart, return cart, or user token via the specified callback URL.

```http title="Example of a token retrieval request"
GET /your-callback-endpoint/userKey HTTP/1.1
Host: your.callback.url
X-Api-Key: YourApiKey
```

Replace `/your-callback-endpoint`, `your.callback.url`, `userKey`, and `YourSecurityKey` with your actual endpoint, user key, callback URL, and security key, respectively.

```http title="Example of a Cart retrieval request"
GET /your-callback-endpoint/cartId HTTP/1.1
Host: your.callback.url
X-Api-Key: YourApiKey
```

Replace `/your-callback-endpoint`, `your.callback.url`, `cartId`, and `YourSecurityKey` with your actual endpoint, cartId, callback URL, and security key, respectively.

### Security considerations

- Ensure your callback URL is HTTPS-enabled to secure data transmission.
- Keep your security key confidential to prevent unauthorized access.

### Troubleshooting

If you have any issues:

- Ensure that your callback URL is entered correctly.
- Verify that your security key matches the one registered in the application.

## Related pages

- [Area overview page with navigation](/instore.md)
- [Previous page: Map Custom Fields](/instore/implement-instore/integrate-with-instore/map-custom-fields.md)
- [Next page: Use Webhooks](/instore/implement-instore/integrate-with-instore/webhooks.md)
- [Search documentation and API specs](/search.md)