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

# CrossmintOtpDeliveryChannel

> Flutter Enum

**Enum**

OTP delivery channel for phone signers. The enum names are the wire values sent to the signer service — do not rename them.

```dart theme={null}
enum CrossmintOtpDeliveryChannel
```

The channel travels with every onboarding request. The service delivers
by SMS when none is requested and does not persist the choice, so it has
to be supplied again each time the phone signer is selected.