Documented unicity rules in INSTALLED_APPS.

Default: ``()`` (Empty tuple)

A tuple of strings designating all applications that are enabled in this

Django installation. Each string should be a full Python path to an

application configuration class or to a Python package containing a

application. :doc:`Learn more about applications </ref/applications>`.

Django installation. Each string should be a dotted Python path to:

* an application configuration class, or

* a package containing a application.

:doc:`Learn more about application configurations </ref/applications>`.

.. versionchanged:: 1.7

.. admonition:: Use the application registry for introspection

    Your code should never access :setting:`INSTALLED_APPS` directly. Use the

    app registry, :attr:`django.apps.apps`, instead.

    Your code should never access :setting:`INSTALLED_APPS` directly. Use

    :attr:`django.apps.apps` instead.

.. admonition:: Application names and labels must be unique in

                :setting:`INSTALLED_APPS`

    Application :attr:`names <django.apps.AppConfig.name>` — the dotted Python

    path to the application package — must be unique. There is no way to

    include the same application twice, short of duplicating its code under

    another name.

.. admonition:: Application labels must be unique

    Application :attr:`labels <django.apps.AppConfig.label>` — by default the

    final part of the name — must be unique too. For example, you can't

    include both ``django.contrib.auth`` and ``myproject.auth``. However, you

    can relabel an application with a custom configuration that defines a

    different :attr:`~django.apps.AppConfig.label`.

    Application labels (that is, the final part of the dotted path to

    application packages) *must* be unique in :setting:`INSTALLED_APPS`.

    For example, you can't include both ``django.contrib.auth`` and

    ``myproject.auth``.

    These rules apply regardless of whether :setting:`INSTALLED_APPS`

    references application configuration classes on application packages.

.. setting:: INTERNAL_IPS