Chapter 5: Django 404 (page not found)

What Actually Happens When Django Returns 404?

1. User requests a URL (e.g. /polls/this-question-does-not-exist/)
2. Django checks all patterns in urls.py (project + included apps)
3. No match → Django raises Http404 exception internally
4. Django catches it and looks for a custom 404 handler
5. If nothing custom → shows default “Not Found” debug page (DEBUG=True) or plain white “404 Not Found” (DEBUG=False)

Goal today: Replace both the ugly debug page and the boring server default with your own beautiful, branded 404 page.

Step 1: Create the 404 Template (Simplest & Most Common Way)

Django automatically looks for a file called 404.html in these locations (in order):

1. Folders in TEMPLATES[‘DIRS’] (your project-level templates/ folder)
2. Each app’s templates/ subfolder

Recommended place: project-level templates/404.html

Create it:

Now mysite/templates/404.html:

• Extends your base.html → keeps header, nav, footer consistent
• Friendly tone (Hyderabad style 😄)
• Clear call-to-actions (home + polls list)

Step 2: Make Sure Django Finds It (settings.py)

In mysite/settings.py → make sure:

If ‘DIRS’ is empty → Django won’t look in project-level templates/

Step 3: Test It (Two Ways)

Way A – DEBUG = True (development)

Just visit a wrong URL:

http://127.0.0.1:8000/polls/non-existing-slug/

→ You should see your custom 404.html instead of the yellow Django debug page

Way B – DEBUG = False (production simulation)

Temporarily set in settings.py:

Visit same wrong URL → should show your 404 page (not the plain “Not Found” text)

Important: After testing → set DEBUG = True back!

Step 4: Bonus – Custom 404 View (When You Want Logic)

Most projects don’t need this — the template is enough.

But if you want (e.g. log 404s, show suggested polls, etc.):

In mysite/views.py (create file if missing):

In mysite/urls.py (at the very bottom):

Now Django calls your view instead of auto-template lookup.

When to use custom view:

• Want to pass extra context (suggested articles, search form…)
• Log 404s to analytics/sentry
• Show different 404 for logged-in vs anonymous

Most people (including me in 2026): just use 404.html template — simpler.

Step 5: Also Prepare 500.html (Server Error)

Create templates/500.html — same style:

Django auto-uses 500.html when DEBUG=False and a server error occurs.

Quick Checklist – Did You Do It Right?

• templates/404.html exists
• TEMPLATES[‘DIRS’] includes BASE_DIR / ‘templates’
• Extends base.html (keeps navigation & design)
• Tested with wrong URL → custom page shows
• Tested with DEBUG=False → still looks good

Common “Why Is It Not Working?” Moments

Your Quick Task Right Now

1. Create templates/404.html as shown
2. Visit a nonsense URL (e.g. /polls/iamnotreal/ or /random-page/)
3. Confirm your nice branded 404 appears
4. (Optional) Temporarily set DEBUG=False, test again, revert back

Tell me what’s next:

• “It works! Now show me custom 500 page + error logging”
• “How to make 404 suggest similar polls or search?”
• “I want funny 404 messages that change randomly”
• “Got wrong page / still debug screen – here’s what I see”
• Or finally ready for: “Let’s finish voting – POST form + F() increment”

You’ve just made your app much more user-friendly — small detail, big difference. You’re doing really well — let’s keep going! 🚀🇮🇳