JWT Authentication in Flutter: Complete Guide with Example

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When building modern mobile apps, secure authentication and API communication are critical. One of the most widely used solutions for this…

When building modern mobile apps, secure authentication and API communication are critical. One of the most widely used solutions for this is JWT (JSON Web Token) authentication.

In Flutter, JWT is commonly used when your app communicates with a backend API that requires secure token-based login. JWT allows you to authenticate users, authorize actions, and protect data efficiently.

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🔑 What is JWT?

JWT (JSON Web Token) is an open standard (RFC 7519) used for securely transmitting information between parties as a JSON object.

A JWT has three parts:

1. Header — Contains algorithm & token type.
2. Payload — Contains user data (claims like user ID, role).
3. Signature — Verifies the token is not tampered with.

Example JWT:

xxxxx.yyyyy.zzzzz

⚙️ Why Use JWT in Flutter?

• ✅ Secure API communication — Protects sensitive endpoints.
• ✅ Stateless Authentication — No need to store sessions on server.
• ✅ Role-based Access — Admin vs User permissions.
• ✅ Cross-platform — Works on web, Android, and iOS.

🛠 Example: JWT Authentication in Flutter

Here's a basic JWT authentication flow with a Node.js backend.

Step 1: Add Dependencies in pubspec.yaml

dependencies:
  http: latest_version
  flutter_secure_storage: latest_version
  jwt_decoder: latest_version

Step 2: Login and Store JWT

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:flutter_secure_storage/flutter_secure_storage.dart';
class JwtAuthExample extends StatefulWidget {
  @override
  _JwtAuthExampleState createState() => _JwtAuthExampleState();
}
class _JwtAuthExampleState extends State<JwtAuthExample> {
  final storage = FlutterSecureStorage();
  String? token;
  Future<void> loginUser() async {
    final response = await http.post(
      Uri.parse("https://your-backend.com/api/login"),
      body: {"email": "test@example.com", "password": "mypassword"},
    );
    if (response.statusCode == 200) {
      final data = jsonDecode(response.body);
      token = data["token"];
      await storage.write(key: "jwt", value: token);
      print("JWT Stored: $token");
    } else {
      print("Login failed");
    }
  }
  Future<void> getProtectedData() async {
    final jwt = await storage.read(key: "jwt");
    final response = await http.get(
      Uri.parse("https://your-backend.com/api/protected"),
      headers: {"Authorization": "Bearer $jwt"},
    );
    if (response.statusCode == 200) {
      print("Protected data: ${response.body}");
    } else {
      print("Unauthorized");
    }
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("JWT Authentication")),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(onPressed: loginUser, child: Text("Login & Get JWT")),
            ElevatedButton(onPressed: getProtectedData, child: Text("Access Protected API")),
          ],
        ),
      ),
    );
  }
}

✅ This example demonstrates:

• User login
• JWT received from backend
• JWT stored securely with flutter_secure_storage
• Token used in Authorization header for API requests

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