Add authentication

The next feature you will be adding is authentication.

Authentication with Amplify

Amplify uses Amazon Cognito as its authentication provider. Amazon Cognito is a robust user directory service that handles user registration, authentication, account recovery & other operations. In this tutorial, you'll learn how to add authentication to your application using Amazon Cognito and username/password login.

Create authentication service

To add authentication to your app, run this command:

amplify add auth

Select the defaults for the following prompts:

? Do you want to use the default authentication and security configuration? Default configuration
Warning: you will not be able to edit these selections.
? How do you want users to be able to sign in? Username
? Do you want to configure advanced settings? No, I am done.

To deploy the service, run the push command:

amplify push

✔ Are you sure you want to continue? (Y/n) · yes

Now, the authentication service has been deployed and you can start using it. To view the deployed services in your project at any time, go to Amplify Console by running the following command:

amplify console

Now that you have your authentication service deployed to AWS, it's time to add authentication to your app. Creating a login flow can be quite difficult and time consuming to get right. Luckily, Amplify UI has an Authenticator component that provides an entire authentication flow for you, using the configuration you specified in amplifyconfiguration.json.

Install Amplify UI

The @aws-amplify/ui-react-native package includes React Native specific UI components you'll use to build your app. Install it with the following command:

expo install @aws-amplify/ui-react-native react-native-safe-area-context

npm install @aws-amplify/ui-react-native react-native-safe-area-context

You will also need to install the pod dependencies for iOS:

npx pod-install

After installing pod dependencies, rebuild the app:

npm run ios

Add the Amplify UI Authenticator component

Open App.js and make the following changes:

Open App.tsx and make the following changes:

Import the withAuthenticator Higher-Order Component and useAuthenticator hook:

  withAuthenticator,
  useAuthenticator
} from '@aws-amplify/ui-react-native';

Create a custom SignOutButton component that will be used within the App component and only re-render when its user context changes. Destructure the user and signOut properties returned from the hook.

// retrieves only the current value of 'user' from 'useAuthenticator'
const userSelector = (context) => [context.user];
const SignOutButton = () => {
  const { user, signOut } = useAuthenticator(userSelector);
    <Pressable onPress={signOut} style={styles.buttonContainer}>
      <Text style={styles.buttonText}>
        Hello, {user.username}! Click here to sign out!
      </Text>
    </Pressable>

Add the SignOutButton component to your App component inside of the containers you defined in the last section:

  <SafeAreaView style={styles.container}>
    <View style={styles.container}>
      <SignOutButton />
    </View>
  </SafeAreaView>

Lastly, wrap your App export with the withAuthenticator Amplify UI component:

export default withAuthenticator(App);

Run the app to see the new authentication flow protecting the app:

npm start

Now you should see the app load with an authentication flow allowing users to sign up and sign in. Below you can find a full sample of the code:

import React, { useEffect, useState } from 'react';
  StyleSheet,
  TextInput,
  Pressable,
  SafeAreaView
} from 'react-native';
import { generateClient } from 'aws-amplify/api';
import { createTodo } from './src/graphql/mutations';
import { listTodos } from './src/graphql/queries';
  withAuthenticator,
  useAuthenticator
} from '@aws-amplify/ui-react-native';
import { Amplify } from 'aws-amplify';
import config from './src/amplifyconfiguration.json';
Amplify.configure(config);
// retrieves only the current value of 'user' from 'useAuthenticator'
const userSelector = (context) => [context.user];
const SignOutButton = () => {
  const { user, signOut } = useAuthenticator(userSelector);
    <Pressable onPress={signOut} style={styles.buttonContainer}>
      <Text style={styles.buttonText}>
        Hello, {user.username}! Click here to sign out!
      </Text>
    </Pressable>
const initialFormState = { name: '', description: '' };
const client = generateClient();
const App = () => {
  const [formState, setFormState] = useState(initialFormState);
  const [todos, setTodos] = useState([]);
  useEffect(() => {
    fetchTodos();
  function setInput(key, value) {
    setFormState({ ...formState, [key]: value });
  async function fetchTodos() {
      const todoData = await client.graphql({
        query: listTodos
      const todos = todoData.data.listTodos.items;
      setTodos(todos);
    } catch (err) {
      console.log('error fetching todos');
  async function addTodo() {
      if (!formState.name || !formState.description) return;
      const todo = { ...formState };
      setTodos([...todos, todo]);
      setFormState(initialFormState);
      await client.graphql({
        query: createTodo,
        variables: { input: todo }
    } catch (err) {
      console.log('error creating todo:', err);
    <SafeAreaView style={styles.container}>
      <View style={styles.container}>
        <SignOutButton />
        <TextInput
          onChangeText={(value) => setInput('name', value)}
          style={styles.input}
          value={formState.name}
          placeholder="Name"
        <TextInput
          onChangeText={(value) => setInput('description', value)}
          style={styles.input}
          value={formState.description}
          placeholder="Description"
        <Pressable onPress={addTodo} style={styles.buttonContainer}>
          <Text style={styles.buttonText}>Create todo</Text>
        </Pressable>
        {todos.map((todo, index) => (
          <View key={todo.id ? todo.id : index} style={styles.todo}>
            <Text style={styles.todoName}>{todo.name}</Text>
            <Text style={styles.todoDescription}>{todo.description}</Text>
          </View>
        ))}
      </View>
    </SafeAreaView>
export default withAuthenticator(App);
const styles = StyleSheet.create({
  container: { width: 400, flex: 1, padding: 20, alignSelf: 'center' },
  todo: { marginBottom: 15 },
    backgroundColor: '#ddd',
    marginBottom: 10,
    padding: 8,
    fontSize: 18
  todoName: { fontSize: 20, fontWeight: 'bold' },
  buttonContainer: {
    alignSelf: 'center',
    backgroundColor: 'black',
    paddingHorizontal: 8
  buttonText: { color: 'white', padding: 16, fontSize: 18 }

import React, { useEffect, useState } from 'react';
  StyleSheet,
  TextInput,
  Pressable,
  SafeAreaView
} from 'react-native';
import { generateClient } from 'aws-amplify/api';
import { createTodo } from './src/graphql/mutations';
import { listTodos } from './src/graphql/queries';
  withAuthenticator,
  useAuthenticator
} from '@aws-amplify/ui-react-native';
// retrieves only the current value of 'user' from 'useAuthenticator'
const userSelector = (context) => [context.user];
const SignOutButton = () => {
  const { user, signOut } = useAuthenticator(userSelector);
    <Pressable onPress={signOut} style={styles.buttonContainer}>
      <Text style={styles.buttonText}>
        Hello, {user.username}! Click here to sign out!
      </Text>
    </Pressable>
const initialFormState = { name: '', description: '' };
const client = generateClient();
const App = () => {
  const [formState, setFormState] = useState(initialFormState);
  const [todos, setTodos] = useState([]);
  useEffect(() => {
    fetchTodos();
  function setInput(key, value) {
    setFormState({ ...formState, [key]: value });
  async function fetchTodos() {
      const todoData = await client.graphql({
        query: listTodos
      const todos = todoData.data.listTodos.items;
      setTodos(todos);
    } catch (err) {
      console.log('error fetching todos');
  async function addTodo() {
      if (!formState.name || !formState.description) return;
      const todo = { ...formState };
      setTodos([...todos, todo]);
      setFormState(initialFormState);
      await client.graphql({
        query: createTodo,
        variables: { input: todo }
    } catch (err) {
      console.log('error creating todo:', err);
    <SafeAreaView style={styles.container}>
      <View style={styles.container}>
        <SignOutButton />
        <TextInput
          onChangeText={(value) => setInput('name', value)}
          style={styles.input}
          value={formState.name}
          placeholder="Name"
        <TextInput
          onChangeText={(value) => setInput('description', value)}
          style={styles.input}
          value={formState.description}
          placeholder="Description"
        <Pressable onPress={addTodo} style={styles.buttonContainer}>
          <Text style={styles.buttonText}>Create todo</Text>
        </Pressable>
        {todos.map((todo, index) => (
          <View key={todo.id ? todo.id : index} style={styles.todo}>
            <Text style={styles.todoName}>{todo.name}</Text>
            <Text style={styles.todoDescription}>{todo.description}</Text>
          </View>
        ))}
      </View>
    </SafeAreaView>
export default withAuthenticator(App);
const styles = StyleSheet.create({
  container: { width: 400, flex: 1, padding: 20, alignSelf: 'center' },
  todo: { marginBottom: 15 },
    backgroundColor: '#ddd',
    marginBottom: 10,
    padding: 8,
    fontSize: 18
  todoName: { fontSize: 20, fontWeight: 'bold' },
  buttonContainer: {
    alignSelf: 'center',
    backgroundColor: 'black',
    paddingHorizontal: 8
  buttonText: { color: 'white', padding: 16, fontSize: 18 }

Using Amplify UI connected components makes it easier to manage styling across your entire app.

In this example, you used the Amplify UI library and the withAuthenticator Higher-Order Component to quickly get up and running with a real-world authentication flow. You can also customize this component to add or remove fields, update styling, or other configurations. You can even override function calls if needed. To learn more, visit the Amplify UI documentation website.

In addition to withAuthenticator, you can build custom authentication flows with the Amplify Library for JS. Amplify's Auth package has several methods including signUp, signIn, forgotPassword, and signOut that allow you full control over all aspects of the user authentication flow.

Connect API and database to the app

Next steps

Add authentication

Authentication with Amplify

Create authentication service

Create login UI

Install Amplify UI

Add the Amplify UI Authenticator component