> For the complete documentation index, see [llms.txt](https://docs.cotter.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cotter.app/sdk-reference/flutter/sign-in-with-device.md).

# Sign In with Device

> **Concepts:** Learn about how [**Sign in with Device**](/features/passwordless-login.md) works.

{% hint style="warning" %}
There are major updates planned for this feature. [Contact us in Slack](https://join.slack.com/t/askcotter/shared_invite/zt-dxzf311g-5Mp3~odZNB2DwYaxIJ1dJA) so we can help you prepare for it.
{% endhint %}

### What you're building

![Sign In with Device using Cotter's Flutter SDK](/files/-M9arn7Qne8dqUy2XJOi)

### Import Cotter as a dependency

Add Cotter to your `pubspec.yaml` , then run `flutter pub get`.

```yaml
dependencies:
  cotter:
```

Check the latest releases in [pub.dev](https://pub.dev/packages/cotter#-installing-tab-). You may need to restart your flutter for it to run pod install (stop flutter run and re run it).

**For Android**: Update `minSdkVersion` to `18` [following the installation instructions](/sdk-reference/flutter.md).

### Step 1: Import and Initialize Cotter

Import Cotter in your `lib/main.dart`, then initialize it inside `HomePageState`.

```dart
import 'package:cotter/cotter.dart'; // Import Cotter

class HomePageState extends State {
  ...

  // 1️⃣ Initialize Cotter
  Cotter cotter = new Cotter(apiKeyID: API_KEY_ID); // 👈 Specify your API KEY ID here

  // 2️⃣ TODO: Make Sign Up Function
  // 3️⃣ TODO: Make Login Function
  
  @override
  Widget build(BuildContext context) { ... }
}
```

You can [create a free account at Cotter](https://dev.cotter.app) to get your `API_KEY_ID`.

{% hint style="info" %}
**Make sure you allow Trusted Devices Method in the** [**dashboard**](https://dev.cotter.app)**.**
{% endhint %}

### Step 2: Make a Sign Up Function

To sign up, call `cotter.signUpWithDevice` and input the user's email. This will create a new user in Cotter and trust the current device to allow logins. This function returns the [User object](/api-reference/user-api/user-object.md).

```dart
  // 2️⃣  Make Sign Up Function
  void signUp(BuildContext context) async {
    try {
      // 🚀 One-line Sign Up
      // Create a new user in Cotter and trust the current device
      var user = await cotter.signUpWithDevice(identifier: inputController.text);
      print(user);
    } catch (e) {
      print(e);
    }
  }
```

#### (Optional) You can also verify the user's email or phone number at this step

To verify the user's email or phone number, follow this guide **after you've finished this one**.

{% content-ref url="/pages/-MAYBXzMAs8ZfSEUGux-" %}
[Add Email/Phone Verification](/sdk-reference/flutter/sign-in-with-device/add-email-phone-verification.md)
{% endcontent-ref %}

### Step 3: Make a Login Function

To sign in, call `cotter.signInWithDevice` . If the user is logging-in from a device that they trust, they'll automatically be approved. This function returns the [Event object](/api-reference/event-object.md).

```dart
  // 3️⃣  Make Login Function
  void login(BuildContext context) async {
    try {
      // 🚀 One-line Login
      var event = await cotter.signInWithDevice(identifier: inputController.text, context: context);
      print(event);
    } catch (e) {
      print(e);
    }
  }
```

#### To get the Logged-in User Info and Access Token, follow this section:

{% content-ref url="/pages/-M9axG8HPu6f\_at6wCcT" %}
[Getting OAuth Tokens](/sdk-reference/flutter/getting-oauth-tokens.md)
{% endcontent-ref %}

{% content-ref url="/pages/-M9awQf5uqyq2X9ZO4JM" %}
[Getting the Logged-in User](/sdk-reference/flutter/getting-the-logged-in-user.md)
{% endcontent-ref %}

#### Logging-in From a Trusted Device

If the user logged-in from a trusted device, their login request will automatically be approved.

#### Logging-in From a Non-Trusted Device

If the user logged-in from a different device that is not trusted, they will be presented with a prompt asking them to approve the login from their trusted phone inside your app. We'll cover this in the next guide.

## Validating Cotter's Access Token 

Checkout how to verify the OAuth Tokens from Cotter here:

{% content-ref url="/pages/-M4HZPVawEx2QN3qLmnv" %}
[Verifying JWT Tokens](/getting-access-token/verifying-jwt-tokens.md)
{% endcontent-ref %}

## 🎉 You're done! <a href="#youre-done" id="youre-done"></a>

### Add Email/Phone Verification

You can also verify your user's email or phone number during the sign up process.

{% content-ref url="/pages/-MAYBXzMAs8ZfSEUGux-" %}
[Add Email/Phone Verification](/sdk-reference/flutter/sign-in-with-device/add-email-phone-verification.md)
{% endcontent-ref %}

### Getting the Logged-in User

Cotter's SDK automatically saves the logged-in user in your device's secure storage. Check out how to get the user information:

{% content-ref url="/pages/-M9awQf5uqyq2X9ZO4JM" %}
[Getting the Logged-in User](/sdk-reference/flutter/getting-the-logged-in-user.md)
{% endcontent-ref %}

### Getting OAuth Tokens

Cotter also automatically generates an `access_token`, `id_token` , and `refresh_token` that is securely stored in the device's secure storage. Check how to get these tokens:

{% content-ref url="/pages/-M9axG8HPu6f\_at6wCcT" %}
[Getting OAuth Tokens](/sdk-reference/flutter/getting-oauth-tokens.md)
{% endcontent-ref %}