The Ultimate Guide to User Authentication: How to Securely Connect Your Frontend to a Django REST API with Simple JWT

Securing an API is one of the most critical and confusing steps in full-stack development. I know this because I’ve been there—staring at my frontend wondering why it wasn’t talking to the backend. In this guide, I’ll walk you through how I finally figured out how to securely authenticate users between a React frontend and a Django REST API using Simple JWT.

Whether you're building a new web app or fixing a broken login flow, I’ve been in your shoes. I’ll walk you through everything—from why we don’t use sessions in this context to setting up secure endpoints using JSON Web Tokens (JWT). By the end of this guide, you’ll have a solid, secure foundation for handling user authentication in your own project.

🔐 Why Not Sessions?

When I first started with Django, I used sessions and cookies because that’s what Django recommends out of the box. But things got tricky once I started building frontend apps with React. Sessions require server-side storage and rely heavily on cookies, which don't play nicely with modern SPAs (single-page applications) running on different domains or ports.

What I needed was stateless, scalable authentication.

That’s when I discovered Simple JWT—a package that makes it easy to implement token-based authentication for Django REST APIs. Instead of maintaining sessions, you send a token in the Authorization header, and the backend validates it. Clean and scalable.

⚙️ Installing and Configuring Django REST Framework & Simple JWT

Here’s how I set it up step by step.

Step 1: Install required packages

pip install djangorestframework
pip install djangorestframework-simplejwt

File Structure

Then, in your settings.py, make sure the following are included:

INSTALLED_APPS = [
    ...
    'rest_framework',
]

REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework_simplejwt.authentication.JWTAuthentication',
    ),
}

You’re telling Django REST Framework (DRF) to expect JWT tokens in the Authorization header by default.

🔑 Creating Login and Token Endpoints

The next step is setting up endpoints to allow users to log in and get their token. Simple JWT makes this incredibly straightforward.

Add this to your urls.py file:

from django.urls import path
from rest_framework_simplejwt.views import (
    TokenObtainPairView,
    TokenRefreshView,
)

urlpatterns = [
    path('api/token/', TokenObtainPairView.as_view(), name='token_obtain_pair'),
    path('api/token/refresh/', TokenRefreshView.as_view(), name='token_refresh'),
]

Now, when a user logs in by posting their username and password to /api/token/, they receive an access token and a refresh token.

Example payload:

{
  "username": "myuser",
  "password": "mypassword"
}

Example response:

{
  "access": "eyJ0eXAiOiJKV1QiLCJhbGciOi...",
  "refresh": "eyJ0eXAiOiJKV1QiLCJhbGciOi..."
}

I used this in production for a freelance job where I built a mini task management app. The client wanted users to sign in securely and interact with the backend from a React app—and Simple JWT delivered.

💻 Frontend Logic: Storing and Using the Token

Here’s the part that tripped me up initially: how to handle the token on the frontend. Here’s how I eventually got it working:

🔐 Step 1: Storing the Token

In React (or plain JavaScript), I store the token in localStorage for simplicity during development:

localStorage.setItem("access_token", response.data.access);

⚠️ Security Tip: For production apps, consider using HttpOnly cookies instead of localStorage to avoid XSS vulnerabilities.

📡 Step 2: Sending Requests with Authorization

For every protected request to the backend, include the token in the Authorization header.

axios.get("http://localhost:8000/api/tasks/", {
  headers: {
    Authorization: `Bearer ${localStorage.getItem("access_token")}`,
  },
})
.then(response => {
  console.log(response.data);
})
.catch(error => {
  console.error("Unauthorized!", error);
});

I used this exact method in my frontend, and it worked like magic after so much trial and error.

🔒 Protecting Your Django API Endpoints

Now that users have access tokens, you need to protect your views so only authenticated users can use them.

In Django REST Framework, this is done using permission_classes.

Here’s how I locked down my task API views:

from rest_framework.permissions import IsAuthenticated
from rest_framework import generics
from .models import Task
from .serializers import TaskSerializer

class TaskListCreateView(generics.ListCreateAPIView):
    queryset = Task.objects.all()
    serializer_class = TaskSerializer
    permission_classes = [IsAuthenticated]

class TaskDetailView(generics.RetrieveUpdateDestroyAPIView):
    queryset = Task.objects.all()
    serializer_class = TaskSerializer
    permission_classes = [IsAuthenticated]

Now, if a request doesn’t include a valid token, it returns 401 Unauthorized

⚠️ Common Pitfalls and Fixes

Here are a few roadblocks I ran into—and how I solved them:

1. CORS Errors

React runs on a different port from Django. This triggers CORS (Cross-Origin Resource Sharing) issues.

Solution:

pip install django-cors-headers

In settings.py:

INSTALLED_APPS = [
    ...
    'corsheaders',
]

MIDDLEWARE = [
    'corsheaders.middleware.CorsMiddleware',
    ...
]

CORS_ALLOWED_ORIGINS = [
    "http://localhost:3000",
]

2. Token Expiry

Access tokens expire fast. Use the refresh token to get a new one:

axios.post("http://localhost:8000/api/token/refresh/", {
  refresh: localStorage.getItem("refresh_token")
})
.then(response => {
  localStorage.setItem("access_token", response.data.access);
});

✅ Final Flow Recap

Here’s what a successful secure login flow looks like in my project:

1. User logs in → Frontend posts credentials to /api/token/

2. Django returns access + refresh tokens

3. Frontend stores tokens

4. Subsequent requests include Authorization: Bearer <access_token>

5. Backend validates token and allows access

6. If token expires, frontend uses refresh token to get a new one

🧠 Final Thoughts (and Bonus: Get the Code!)

User authentication can be confusing, especially across frontend and backend systems. But once you understand the flow—and the role Simple JWT plays—it becomes manageable and repeatable.

I’ve packaged this entire setup in a GitHub repo you can clone and play with:

🔗 Check the code on GitHub 

🔗 Check the video work through 

Whether you’re building a SaaS app, internal tool, or just learning full-stack development, securing your API with JWT is a must-know skill.

Got stuck? Drop me a message. I’ve been there, and I’m here to help.