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

# SDK Callback Flow

> Guide to understand the callback flow of the SDK

### 1. SDK Initialization Flow

The following diagram illustrates the initialization sequence for Otpless SDK.

<img src="https://mintcdn.com/otpless-96/MG5MLCTUP00EUtvA/images/sdk-init-flow.png?fit=max&auto=format&n=MG5MLCTUP00EUtvA&q=85&s=7e8efbc709afaa22413f50b61945a71d" width="1607" height="1496" data-path="images/sdk-init-flow.png" />

### 2. Headless Authentication Flow (SNA)

The following diagram illustrates the authentication sequence for Otpless SDK.

<img src="https://mintcdn.com/otpless-96/MG5MLCTUP00EUtvA/images/ios-auth-flow1.png?fit=max&auto=format&n=MG5MLCTUP00EUtvA&q=85&s=7fbe852d51ada0003246500e4bd91620" width="3840" height="3598" data-path="images/ios-auth-flow1.png" />

### 2. Headless Authentication Flow (OTP)

The following diagram illustrates the authentication sequence for Otpless SDK.

<img src="https://mintcdn.com/otpless-96/MG5MLCTUP00EUtvA/images/ios-auth-flow2.png?fit=max&auto=format&n=MG5MLCTUP00EUtvA&q=85&s=b1d26791f738d5618bd297a60e4ee4d5" width="3158" height="3840" data-path="images/ios-auth-flow2.png" />