Handling Django Authentication Redirects in HTMX Applications

02 May, 2025

Ever been in the middle of building a slick Django app with HTMX when you hit that authentication headache? You know the one - a user’s session times out, they click something, and instead of getting a proper login page, they get a weird login form fragment jammed into whatever DOM element was being updated. Not exactly the seamless experience we’re going for!

I ran into this problem recently and thought, “There’s got to be a better way.” Spoiler alert: there is! Let me show you a simple middleware solution that makes this authentication dance much smoother.

What’s Going Wrong?

HTMX is fantastic for making our web apps feel snappy with those partial page updates. But here’s the issue: when a user’s session expires and they click an HTMX-powered button, Django tries to redirect them to the login page. The problem? HTMX doesn’t know any better, so it tries to swap that login page HTML into whatever element was targeted - maybe just a tiny div or table cell. The result is a mess - login forms crammed into weird places, broken layouts, and confused users.

What we really want is to redirect the whole browser to the login page, and then bring users right back to where they were after they log in again. Simple idea, slightly tricky execution.

The Fix: A Bit of Middleware Magic

Here’s my solution - a small but mighty piece of middleware that catches those authentication redirects and tells HTMX, “Hey, don’t just swap in that content, take me to a whole new page!” The best part? It remembers where you were trying to go, so you’ll end up right back where you wanted after logging in. Check it out:

from urllib.parse import urlparse


class HtmxAuthRedirectMiddleware:
    """
    Middleware to handle HTMX authentication redirects properly.

    When an HTMX request results in a 302 redirect (typically for authentication),
    this middleware:
    1. Changes the response status code to 204 (No Content)
    2. Adds an HX-Redirect header with the redirect URL
    3. Preserves the original request path in the 'next' query parameter

    This ensures that after authentication, the user is returned to the page
    they were attempting to access, maintaining a seamless UX with HTMX.

    Credits: https://www.caktusgroup.com/blog/2022/11/11/how-handle-django-login-redirects-htmx/
    """

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

    def __call__(self, request):
        response = self.get_response(request)
        # HTMX request returning 302 likely is login required.
        # Take the redirect location and send it as the HX-Redirect header value,
        # with 'next' query param set to where the request originated. Also change
        # response status code to 204 (no content) so that htmx will obey the
        # HX-Redirect header value.
        if request.headers.get("HX-Request") == "true" and response.status_code == 302:
            # Determine the next path from referer or current request path
            ref_header = request.headers.get("Referer", "")
            if ref_header:
                referer = urlparse(ref_header)
                next_path = referer.path
            else:
                next_path = request.path

            # Parse the redirect URL
            redirect_url = urlparse(response["location"])

            # Set response status code to 204 for HTMX to process the redirect
            response.status_code = 204

            # Update the "?next" query parameter
            query_params = parse_qs(redirect_url.query)
            query_params["next"] = [next_path]
            new_query = urlencode(query_params, doseq=True)

            # Set the new HX-Redirect header
            response.headers["HX-Redirect"] = f"{redirect_url.path}?{new_query}"

        return response

This middleware is inspired by this post by the caktus group.

So How Does This Thing Work?

Let me break down what this middleware is doing in plain English:

Spotting the Problem: It watches for HTMX requests that get a “redirect to login” response (that’s the 302 status code).
Changing the Signal: Instead of letting that redirect happen normally, it changes the response to a “204 No Content” - which is basically telling HTMX, “Hey, wait a sec, check the headers for special instructions.”
The Magic Header: It adds an HX-Redirect header that HTMX understands as “redirect the ENTIRE page to this URL” rather than just swapping content.
Breadcrumb Trail: It tucks the original page URL into the next parameter so Django knows where to send the user after they log in.

The cool part is how it handles all the edge cases:

It properly parses URLs to avoid any weirdness with parameters
It’s smart about figuring out where the user was really trying to go (using the referer when available)
It works nicely with existing code that might already be using the next parameter
All this happens invisibly to the user - they just see a smooth transition to login and back

Note: For simplcity this middleware will handle any kind of redirect with a 302 status code, not just authentication redirects. If you project expects something different, you might want to add some extra checks to make sure it’s only handling the right cases.

Adding This to Your Project

Getting this set up is super simple. Just drop the middleware into your Django project and add it to your MIDDLEWARE list in settings.py:

MIDDLEWARE = [
    # Your other middleware stuff...
    'yourapp.middleware.HtmxAuthRedirectMiddleware',
]

Just make sure it comes after Django’s authentication middleware in the list - order matters here!

Why This Makes Your App Better

This little piece of middleware punches above its weight class:

No More Ugly Surprises: Users never see that weird “login form crammed into a table cell” problem.
They Pick Up Right Where They Left Off: After logging in, they land exactly where they were headed.
Zero Extra JavaScript: No need to write any client-side code - it just works.
Keep Your Code Clean: Instead of sprinkling authentication redirect handling all over your views, it’s all in one tidy place.

Wrapping Up

This middleware solution leverages the built-in capabilities of both Django and HTMX to solve authentication redirects elegantly. By connecting Django’s middleware hooks with HTMX’s header-based controls, it eliminates the jarring “login form in wrong place” problem without any custom JavaScript.

Give it a try in your project, and let me know how it works for you! I’m always open to tweaks and improvements.

Happy coding!

Edits:

2025-05-04: Use urlparse and parse_qs to securely handle urls. Thanks Adam Johnson

#Django #Htmx #Authentication #Middleware #Web-Development