> ## Documentation Index
> Fetch the complete documentation index at: https://cometchat-22654f5b-docs-agentbuddy-4.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

> Create users, log in with Auth Key or Auth Token, check login status, and log out using the CometChat iOS SDK.

<Accordion title="AI Integration Quick Reference">
  ```swift theme={null}
  // Check existing session
  let user = CometChat.getLoggedInUser()

  // Login with Auth Key (development only)
  CometChat.login(UID: "cometchat-uid-1", authKey: "AUTH_KEY", onSuccess: { user in
    print("Logged in: \(user.stringValue())")
  }, onError: { error in
    print("Login failed: \(error.errorDescription)")
  })

  // Login with Auth Token (production)
  CometChat.login(authToken: "AUTH_TOKEN", onSuccess: { user in
    print("Logged in: \(user.stringValue())")
  }, onError: { error in
    print("Login failed: \(error.errorDescription)")
  })

  // Logout
  CometChat.logout(onSuccess: { _ in
    print("Logged out")
  }, onError: { error in
    print("Logout failed: \(error.errorDescription)")
  })
  ```

  **Create users via:** [Dashboard](https://app.cometchat.com) (testing) | [REST API](https://api-explorer.cometchat.com/reference/creates-user) (production)
  **Test UIDs:** `cometchat-uid-1` through `cometchat-uid-5`
</Accordion>

After [initializing](/sdk/ios/setup) the SDK, the next step is to authenticate your user. CometChat provides two login methods — Auth Key for quick development, and Auth Token for production — both accessed through the `login()` method.

### How It Works

```mermaid theme={null}
sequenceDiagram
    participant User
    participant YourApp as Your App
    participant YourServer as Your Server
    participant CometChat as CometChat

    User->>YourApp: Signs up / Logs in
    YourApp->>YourServer: Authenticate user
    YourServer->>CometChat: Create user (REST API, first time only)
    CometChat-->>YourServer: User created
    YourServer->>CometChat: Create Auth Token (REST API)
    CometChat-->>YourServer: Auth Token
    YourServer-->>YourApp: Return Auth Token
    YourApp->>CometChat: CometChat.login(authToken:)
    CometChat-->>YourApp: User object (logged in)
```

## Before You Log In

### Create a User

A user must exist in CometChat before they can log in.

* **During development:** Create users from the [CometChat Dashboard](https://app.cometchat.com). Five test users are already available with UIDs `cometchat-uid-1` through `cometchat-uid-5`.
* **In production:** Call the [Create User REST API](https://api-explorer.cometchat.com/reference/creates-user) when a user signs up in your app.

You can also create users from the client side using `createUser()` (development only):

<Tabs>
  <Tab title="Swift">
    ```swift theme={null}
    let authKey = "AUTH_KEY"
    let uid = "user1"
    let name = "Kevin"

    let newUser = User(uid: uid, name: name)

    CometChat.createUser(user: newUser, apiKey: authKey, onSuccess: { (user) in
      print("User created: \(user.stringValue())")
    }) { (error) in
      print("Error: \(String(describing: error?.description))")
    }
    ```
  </Tab>

  <Tab title="Objective-C">
    ```objc theme={null}
    NSString *authKey = @"AUTH_KEY";
    User *newUser = [[User alloc] initWithUid:@"user1" name:@"Kevin"];

    [CometChat createUserWithUser:newUser apiKey:authKey onSuccess:^(User * user) {
      NSLog(@"User created: %@", [user stringValue]);
    } onError:^(CometChatException * error) {
      NSLog(@"Error: %@", [error errorDescription]);
    }];
    ```
  </Tab>
</Tabs>

<Warning>
  `createUser()` with Auth Key is for development only. In production, create users server-side via the [REST API](https://api-explorer.cometchat.com/reference/creates-user). See [User Management](/sdk/ios/user-management) for full details.
</Warning>

### Check for an Existing Session

The SDK persists the logged-in user's session locally. Before calling `login()`, always check whether a session already exists — this avoids unnecessary login calls and keeps your app responsive.

```swift theme={null}
if let user = CometChat.getLoggedInUser() {
  // User is already logged in — proceed to your app
}
```

If `getLoggedInUser()` returns `nil`, no active session exists and you need to call `login()`.

## Login with Auth Key

Auth Key login is the simplest way to get started. Pass a UID and your Auth Key directly from the client.

<Warning>
  Auth Keys are meant for development and testing only. For production, use [Auth Token login](#login-with-auth-token) instead. Never ship Auth Keys in client-side code.
</Warning>

<Tabs>
  <Tab title="Swift">
    ```swift theme={null}
    let uid = "cometchat-uid-1"
    let authKey = "AUTH_KEY"

    if CometChat.getLoggedInUser() == nil {
      CometChat.login(UID: uid, authKey: authKey, onSuccess: { (user) in
        print("Login successful: " + user.stringValue())
      }) { (error) in
        print("Login failed with error: " + error.errorDescription)
      }
    }
    ```
  </Tab>

  <Tab title="Objective-C">
    ```objc theme={null}
    NSString *uid = @"cometchat-uid-1";
    NSString *authKey = @"AUTH_KEY";

    [CometChat loginWithUID:uid authKey:authKey onSuccess:^(User * user) {
      NSLog(@"Login successful: %@", [user stringValue]);
    } onError:^(CometChatException * error) {
      NSLog(@"Login failed with error: %@", [error errorDescription]);
    }];
    ```
  </Tab>
</Tabs>

| Parameter | Description                   |
| --------- | ----------------------------- |
| UID       | The UID of the user to log in |
| authKey   | Your CometChat Auth Key       |

On success, the callback returns a [`User`](/sdk/reference/entities#user) object containing the logged-in user's details.

## Login with Auth Token

Auth Token login keeps your Auth Key off the client entirely. Your server generates a token via the REST API and passes it to the client.

1. [Create the user](https://api-explorer.cometchat.com/reference/creates-user) via the REST API when they sign up (first time only).
2. [Generate an Auth Token](https://api-explorer.cometchat.com/reference/create-authtoken) on your server and return it to the client.
3. Pass the token to `login()`.

<Tabs>
  <Tab title="Swift">
    ```swift theme={null}
    let authToken = "AUTH_TOKEN"

    if CometChat.getLoggedInUser() == nil {
      CometChat.login(authToken: authToken, onSuccess: { (user) in
        print("Login successful: " + user.stringValue())
      }) { (error) in
        print("Login failed with error: " + error.errorDescription)
      }
    }
    ```
  </Tab>

  <Tab title="Objective-C">
    ```objc theme={null}
    NSString *authToken = @"AUTH_TOKEN";

    [CometChat loginWithAuthToken:authToken onSuccess:^(User * user) {
      NSLog(@"Login successful: %@", [user stringValue]);
    } onError:^(CometChatException * error) {
      NSLog(@"Login failed with error: %@", [error errorDescription]);
    }];
    ```
  </Tab>
</Tabs>

| Parameter | Description                                      |
| --------- | ------------------------------------------------ |
| authToken | Auth Token generated on your server for the user |

On success, the callback returns a [`User`](/sdk/reference/entities#user) object containing the logged-in user's details.

## Logout

Call `logout()` when your user logs out of your app. This clears the local session.

<Tabs>
  <Tab title="Swift">
    ```swift theme={null}
    CometChat.logout(onSuccess: { (response) in
      print("Logout completed successfully")
    }) { (error) in
      print("Logout failed with error: " + error.errorDescription)
    }
    ```
  </Tab>

  <Tab title="Objective-C">
    ```objc theme={null}
    [CometChat logoutOnSuccess:^(NSString * response) {
      NSLog(@"Logout completed successfully");
    } onError:^(CometChatException * error) {
      NSLog(@"Logout failed: %@", [error errorDescription]);
    }];
    ```
  </Tab>
</Tabs>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Send Messages" icon="paper-plane" href="/sdk/ios/send-message">
    Send your first text, media, or custom message
  </Card>

  <Card title="User Management" icon="users-gear" href="/sdk/ios/user-management">
    Create, update, and delete users programmatically
  </Card>

  <Card title="Connection Status" icon="signal" href="/sdk/ios/connection-status">
    Monitor the SDK connection state in real time
  </Card>

  <Card title="Ringing Calls" icon="phone" href="/sdk/ios/default-calling">
    Implement voice and video calls with ringing
  </Card>
</CardGroup>