# Sign In Blocks

## Overview

Authentication is the process by which your app’s users sign up or sign in to your app. It confirms the legitimacy of a user's identity before allowing them to interact with the application. 

Thunkable supports authentication through:

{% content-ref url="sign-in/sign-in" %}
[sign-in](https://docs.thunkable.com/blocks/app-features/sign-in/sign-in)
{% endcontent-ref %}

{% content-ref url="sign-in/sign-in-1" %}
[sign-in-1](https://docs.thunkable.com/blocks/app-features/sign-in/sign-in-1)
{% endcontent-ref %}

{% content-ref url="sign-in/user-sign-up-sign-in-and-authentication-with-apple" %}
[user-sign-up-sign-in-and-authentication-with-apple](https://docs.thunkable.com/blocks/app-features/sign-in/user-sign-up-sign-in-and-authentication-with-apple)
{% endcontent-ref %}