Django's BrokenLinkEmailsMiddleware can email you about broken links on your site:

Broken link on mysite.com
=========================
Referrer: https://www.google.com
Requested URL: /nonexistent
User agent: Mozilla/5.0 (...)
IP address: 1.2.3.4

The problem is, these emails often contain false positives. To tell Django to ignore particular broken links, you need to change the setting IGNORABLE_404_URLS. This quickly becomes tedious.

This library is a drop-in replacement for BrokenLinkEmailsMiddleware. It sends the same emails, but is configured via the database (and Django's Admin interface) instead of a setting. This makes it much easier to mark URLs as ignorable.

When a broken URL is encountered, this library adds a link to the bottom of the 404 email:

Broken link on mysite.com
=========================
...

To ignore this link, visit mysite.com/admin/...

Clicking on the link opens Django's Admin interface with a pre-filled form for ignoring the 404:

Just click Save to never be notified of this particular false positive again.

Install this library via:

pip install django-404-middleware

Add it to the INSTALLED_APPS in your Django settings file:

INSTALLED_APPS = [
    ...,
    'django_404_middleware'
]

Also add it to your MIDDLEWARE setting. Typically, you would already have an entry django.middleware.common.BrokenLinkEmailsMiddleware. Replace it by the following:

MIDDLEWARE = [
    ...,
    'django_404_middleware.BrokenLinkEmailsDbMiddleware',
    ...
]

(Note that if you are using Django < 2, the setting is called MIDDLEWARE_CLASSES, not MIDDLEWARE.)

The same caveat as for Django's built-in 404 middleware applies: BrokenLinkEmailsDbMiddleware must appear before other middleware that intercepts 404 errors. Put it towards the top of your MIDDLEWARE setting.

Finally, apply migrations to initialise the database:

python manage.py migrate

The current implementation is not optimized for performance in any way.