> ## Documentation Index
> Fetch the complete documentation index at: https://cometchat-22654f5b-docs-rn-guide-message-privately.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Users

> Understand CometChat users in Flutter apps, including UIDs, auth tokens, roles, user lists, friends, and user management.

A user is anyone who uses CometChat. The primary aim for the users functionality is to allow you to quickly retrieve and add users to CometChat.

## UID

* Each user is uniquely identified using a UID.
* The UID is typically the primary ID of the user from your database.

<Warning>
  UID can be alphanumeric with underscore and hyphen. Spaces, punctuation and other special characters are not allowed.
</Warning>

## Auth Token

* A single user can have multiple auth tokens. Auth tokens should be per user per device.
* It should be generated via a server-to-server API call. The auth token should then be passed to CometChat for login.
* An Auth Token can only be deleted via the dashboard or using the REST API.

## User Roles

A role is a category for a group of similar users. For example, you may want to group your premium users using the role "Premium". You then use this to filter users or enable/disable features by writing conditional code.

## User List

* The User List can be used to build the **Contacts** or **Who's Online** view in your app.
* The list of users can be different based on the logged-in user.

## Next Steps

* [User Management](/sdk/flutter/user-management) — sync your users to CometChat
* [Retrieve Users](/sdk/flutter/retrieve-users) — fetch and display users in your app