How to Create Custom Middleware in Django: Simple Guide

To create custom middleware in Django, define a class with an __init__ and a __call__ method that processes requests and responses. Then add your middleware class path to the MIDDLEWARE list in settings.py.

Syntax

A custom middleware in Django is a class with two main parts:

• __init__(self, get_response): Called once when the server starts, it receives the next middleware or view as get_response.
• __call__(self, request): Called on each request, it can modify the request before passing it on and modify the response before returning it.

You return the response object at the end.

python

class CustomMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        # Code before view (request processing)
        response = self.get_response(request)
        # Code after view (response processing)
        return response

Example

This example middleware adds a custom header to every HTTP response.

python

class SimpleHeaderMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        response = self.get_response(request)
        response['X-Custom-Header'] = 'Hello from middleware'
        return response

# Add 'path.to.SimpleHeaderMiddleware' to MIDDLEWARE in settings.py

Output

When you make a request, the HTTP response will include the header:
X-Custom-Header: Hello from middleware

Common Pitfalls

• Not calling get_response(request) inside __call__ will break request processing.
• Modifying the request or response incorrectly can cause errors or unexpected behavior.
• For older Django versions (before 1.10), middleware used a different style; always use the new style middleware.

python

from django.http import HttpResponse

class WrongMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        # Forgot to call get_response
        return HttpResponse('Blocked')  # This stops all views

class CorrectMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        response = self.get_response(request)
        return response

Quick Reference

Steps to create custom middleware:

• Define a class with __init__(self, get_response) and __call__(self, request).
• Process request before calling get_response(request).
• Process response after calling get_response(request).
• Add the middleware class path to MIDDLEWARE in settings.py.

Key Takeaways

Custom middleware is a class with __init__ and __call__ methods to process requests and responses.

Always call get_response(request) inside __call__ to continue processing the request.

Add your middleware class path to the MIDDLEWARE list in settings.py to activate it.

Use the new style middleware introduced in Django 1.10 and later for best compatibility.

Middleware can modify requests before views and responses after views for flexible control.