For example, I've seen methods which design custom views with changes to URLconf, I've seen other methods that use handler404 = "mysite.views.my_custom_page_not_found_view" in URLconf with no changes to views. I've seen both of these methods explained in the docs. The easiest method I've seen is to simply create a templates/404.html without any other changes to the app. So which method is best for a production app?
The answer to this question depends on how big the project is and on the guidelines of your team.
Avoid using urlpatterns. While technically possible, it is not recommended. Error pages shouldn't be directly accessible through a URL, as this goes against their intended purpose. They should be handled automatically by Django when an error occurs.
Now it comes down to two options: templates/404.html or handler404 = "mysite.views.my_custom_page_not_found_view"
Using templates/404.html: Django automatically looks for the 404.html template in your templates directory and serves it for the respective error. This is great for two main reasons:
Using handler404: Define custom views for error handling in your urls.py. This allows you to control and customize the response dynamically based on user or request details, as well as add custom logic (e.g., logging errors, analytics, or personalized messages).
As you can see, your choice depends on understanding your needs: Simplicity VS Control.
Finally, this is something that you and your team should agree on and standardize to maintain consistency across the project.