Django Middleware

Details

Middleware in Django is a series of components that sit between the user's request and your final response. Think of it as a set of filters or checkpoints that inspect or modify the data passing through them.

Each middleware piece has a chance to process what’s going in or coming out of your application.

What Does Middleware Do?

Middleware can:

• Block or allow requests
• Alter responses before they reach the browser
• Handle redirection or error handling
• Inject headers or cookies
• Perform logging or analytics
• Manage authentication behind the scenes

Where Middleware Lives

Middleware is listed in your project’s settings file. Open settings.py and locate the MIDDLEWARE section:

MIDDLEWARE = [     
          'django.middleware.security.SecurityMiddleware',     
          'django.contrib.sessions.middleware.SessionMiddleware',     
          'django.middleware.common.CommonMiddleware',     
           ... 
] 

Each item is a class path. Django runs them from top to bottom when receiving a request, and in reverse order when sending the response back.

Writing Your Own Middleware

To create a custom one, write a class with two methods: __init__() and __call__() or process_*() methods.

Example:

class SimpleLoggerMiddleware:     
       def __init__(self, get_response):         
            self.get_response = get_response      
      
      def __call__(self, request):         
            Print(f"Accessing: {request.path}")         
            response = self.get_response(request)         
            return response 

To activate it, add the path in the MIDDLEWARE list:

members.middleware.SimpleLoggerMiddleware',

Types of Middleware Hooks

There are various points you can plug into:

• process_request(self, request) – runs before view logic
• process_view(self, request, view_func, view_args, view_kwargs) – triggers right before view executes
• process_exception(self, request, exception) – handles errors from views
• process_response(self, request, response) – edits what gets returned

These are optional. You can define only what you need.

Built-in Middleware Examples

Here are a few built-in ones and what they do:

• SessionMiddleware – tracks user sessions
• AuthenticationMiddleware – attaches user data to requests
• CsrfViewMiddleware – guards against cross-site request forgery
• CommonMiddleware – adds useful headers and redirects
• SecurityMiddleware – enforces security-related headers

Order Matters

Since middleware stacks act in sequence, their order in the list changes how your app behaves. For example, authentication should run after sessions are enabled.

Summary

• Middleware runs during both request and response phases
• Each class can inspect, change, or stop requests/responses
• You can use built-ins or create your own
• Add them in settings.py under MIDDLEWARE
• They’re helpful for logging, security, session handling, and more