Customizing authentication in Django

The authentication that comes with Django is good enough for most common cases, but you may have needs not met by the out-of-the-box defaults. Customizing authentication in your projects requires understanding what points of the provided system are extensible or replaceable. This document provides details about how the auth system can be customized.

Authentication backends provide an extensible system for when a username and password stored with the user model need to be authenticated against a different service than Django’s default.

You can give your models custom permissions that can be checked through Django’s authorization system.

You can extend the default User model, or substitute a completely customized model.

Other authentication sources

There may be times you have the need to hook into another authentication source – that is, another source of usernames and passwords or authentication methods.

For example, your company may already have an LDAP setup that stores a username and password for every employee. It’d be a hassle for both the network administrator and the users themselves if users had separate accounts in LDAP and the Django-based applications.

So, to handle situations like this, the Django authentication system lets you plug in other authentication sources. You can override Django’s default database-based scheme, or you can use the default system in tandem with other systems.

See the authentication backend reference for information on the authentication backends included with Django.

Specifying authentication backends

Behind the scenes, Django maintains a list of “authentication backends” that it checks for authentication. When somebody calls django.contrib.auth.authenticate() – as described in How to log a user in – Django tries authenticating across all of its authentication backends. If the first authentication method fails, Django tries the second one, and so on, until all backends have been attempted.

The list of authentication backends to use is specified in the AUTHENTICATION_BACKENDS setting. This should be a list of Python path names that point to Python classes that know how to authenticate. These classes can be anywhere on your Python path.

By default, AUTHENTICATION_BACKENDS is set to:

['django.contrib.auth.backends.ModelBackend']

That’s the basic authentication backend that checks the Django users database and queries the built-in permissions. It does not provide protection against brute force attacks via any rate limiting mechanism. You may either implement your own rate limiting mechanism in a custom auth backend, or use the mechanisms provided by most Web servers.

The order of AUTHENTICATION_BACKENDS matters, so if the same username and password is valid in multiple backends, Django will stop processing at the first positive match.

If a backend raises a PermissionDenied exception, authentication will immediately fail. Django won’t check the backends that follow.

Writing an authentication backend

An authentication backend is a class that implements two required methods: get_user(user_id) and authenticate(request, **credentials), as well as a set of optional permission related authorization methods.

The get_user method takes a user_id – which could be a username, database ID or whatever, but has to be the primary key of your user object – and returns a user object or None.

The authenticate method takes a request argument and credentials as keyword arguments. Most of the time, it’ll look like this:

from django.contrib.auth.backends import BaseBackend

class MyBackend(BaseBackend):
    def authenticate(self, request, username=None, password=None):
        # Check the username/password and return a user.
        ...

But it could also authenticate a token, like so:

from django.contrib.auth.backends import BaseBackend

class MyBackend(BaseBackend):
    def authenticate(self, request, token=None):
        # Check the token and return a user.
        ...

Either way, authenticate() should check the credentials it gets and return a user object that matches those credentials if the credentials are valid. If they’re not valid, it should return None.

request is an HttpRequest and may be None if it wasn’t provided to authenticate() (which passes it on to the backend).

The Django admin is tightly coupled to the Django User object. The best way to deal with this is to create a Django User object for each user that exists for your backend (e.g., in your LDAP directory, your external SQL database, etc.) You can either write a script to do this in advance, or your authenticate method can do it the first time a user logs in.

Here’s an example backend that authenticates against a username and password variable defined in your settings.py file and creates a Django User object the first time a user authenticates:

from django.conf import settings
from django.contrib.auth.backends import BaseBackend
from django.contrib.auth.hashers import check_password
from django.contrib.auth.models import User

class SettingsBackend(BaseBackend):
    """
    Authenticate against the settings ADMIN_LOGIN and ADMIN_PASSWORD.

    Use the login name and a hash of the password. For example:

    ADMIN_LOGIN = 'admin'
    ADMIN_PASSWORD = 'pbkdf2_sha256$30000$Vo0VlMnkR4Bk$qEvtdyZRWTcOsCnI/oQ7fVOu1XAURIZYoOZ3iq8Dr4M='
    """

    def authenticate(self, request, username=None, password=None):
        login_valid = (settings.ADMIN_LOGIN == username)
        pwd_valid = check_password(password, settings.ADMIN_PASSWORD)
        if login_valid and pwd_valid:
            try:
                user = User.objects.get(username=username)
            except User.DoesNotExist:
                # Create a new user. There's no need to set a password
                # because only the password from settings.py is checked.
                user = User(username=username)
                user.is_staff = True
                user.is_superuser = True
                user.save()
            return user
        return None

    def get_user(self, user_id):
        try:
            return User.objects.get(pk=user_id)
        except User.DoesNotExist:
            return None

Handling authorization in custom backends

Custom auth backends can provide their own permissions.

The user model and its manager will delegate permission lookup functions (get_user_permissions(), get_group_permissions(), get_all_permissions(), has_perm(), has_module_perms(), and with_perm()) to any authentication backend that implements these functions.

The permissions given to the user will be the superset of all permissions returned by all backends. That is, Django grants a permission to a user that any one backend grants.

If a backend raises a PermissionDenied exception in has_perm() or has_module_perms(), the authorization will immediately fail and Django won’t check the backends that follow.

A backend could implement permissions for the magic admin like this:

from django.contrib.auth.backends import BaseBackend

class MagicAdminBackend(BaseBackend):
    def has_perm(self, user_obj, perm, obj=None):
        return user_obj.username == settings.ADMIN_LOGIN

This gives full permissions to the user granted access in the above example. Notice that in addition to the same arguments given to the associated django.contrib.auth.models.User functions, the backend auth functions all take the user object, which may be an anonymous user, as an argument.

A full authorization implementation can be found in the ModelBackend class in django/contrib/auth/backends.py, which is the default backend and queries the auth_permission table most of the time.

Authorization for anonymous users

An anonymous user is one that is not authenticated i.e. they have provided no valid authentication details. However, that does not necessarily mean they are not authorized to do anything. At the most basic level, most websites authorize anonymous users to browse most of the site, and many allow anonymous posting of comments etc.

Django’s permission framework does not have a place to store permissions for anonymous users. However, the user object passed to an authentication backend may be an django.contrib.auth.models.AnonymousUser object, allowing the backend to specify custom authorization behavior for anonymous users. This is especially useful for the authors of re-usable apps, who can delegate all questions of authorization to the auth backend, rather than needing settings, for example, to control anonymous access.

Authorization for inactive users

An inactive user is one that has its is_active field set to False. The ModelBackend and RemoteUserBackend authentication backends prohibits these users from authenticating. If a custom user model doesn’t have an is_active field, all users will be allowed to authenticate.

You can use AllowAllUsersModelBackend or AllowAllUsersRemoteUserBackend if you want to allow inactive users to authenticate.

The support for anonymous users in the permission system allows for a scenario where anonymous users have permissions to do something while inactive authenticated users do not.

Do not forget to test for the is_active attribute of the user in your own backend permission methods.

Handling object permissions

Django’s permission framework has a foundation for object permissions, though there is no implementation for it in the core. That means that checking for object permissions will always return False or an empty list (depending on the check performed). An authentication backend will receive the keyword parameters obj and user_obj for each object related authorization method and can return the object level permission as appropriate.

Custom permissions

To create custom permissions for a given model object, use the permissions model Meta attribute.

This example Task model creates two custom permissions, i.e., actions users can or cannot do with Task instances, specific to your application:

class Task(models.Model):
    ...
    class Meta:
        permissions = [
            ("change_task_status", "Can change the status of tasks"),
            ("close_task", "Can remove a task by setting its status as closed"),
        ]

The only thing this does is create those extra permissions when you run manage.py migrate (the function that creates permissions is connected to the post_migrate signal). Your code is in charge of checking the value of these permissions when a user is trying to access the functionality provided by the application (changing the status of tasks or closing tasks.) Continuing the above example, the following checks if a user may close tasks:

user.has_perm('app.close_task')

Extending the existing User model

There are two ways to extend the default User model without substituting your own model. If the changes you need are purely behavioral, and don’t require any change to what is stored in the database, you can create a proxy model based on User. This allows for any of the features offered by proxy models including default ordering, custom managers, or custom model methods.

If you wish to store information related to User, you can use a OneToOneField to a model containing the fields for additional information. This one-to-one model is often called a profile model, as it might store non-auth related information about a site user. For example you might create an Employee model:

from django.contrib.auth.models import User

class Employee(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    department = models.CharField(max_length=100)

Assuming an existing Employee Fred Smith who has both a User and Employee model, you can access the related information using Django’s standard related model conventions:

>>> u = User.objects.get(username='fsmith')
>>> freds_department = u.employee.department

To add a profile model’s fields to the user page in the admin, define an InlineModelAdmin (for this example, we’ll use a StackedInline) in your app’s admin.py and add it to a UserAdmin class which is registered with the User class:

from django.contrib import admin
from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
from django.contrib.auth.models import User

from my_user_profile_app.models import Employee

# Define an inline admin descriptor for Employee model
# which acts a bit like a singleton
class EmployeeInline(admin.StackedInline):
    model = Employee
    can_delete = False
    verbose_name_plural = 'employee'

# Define a new User admin
class UserAdmin(BaseUserAdmin):
    inlines = (EmployeeInline,)

# Re-register UserAdmin
admin.site.unregister(User)
admin.site.register(User, UserAdmin)

These profile models are not special in any way - they are just Django models that happen to have a one-to-one link with a user model. As such, they aren’t auto created when a user is created, but a django.db.models.signals.post_save could be used to create or update related models as appropriate.

Using related models results in additional queries or joins to retrieve the related data. Depending on your needs, a custom user model that includes the related fields may be your better option, however, existing relations to the default user model within your project’s apps may justify the extra database load.

Substituting a custom User model

Some kinds of projects may have authentication requirements for which Django’s built-in User model is not always appropriate. For instance, on some sites it makes more sense to use an email address as your identification token instead of a username.

Django allows you to override the default user model by providing a value for the AUTH_USER_MODEL setting that references a custom model:

AUTH_USER_MODEL = 'myapp.MyUser'

This dotted pair describes the name of the Django app (which must be in your INSTALLED_APPS), and the name of the Django model that you wish to use as your user model.

Using a custom user model when starting a project

If you’re starting a new project, it’s highly recommended to set up a custom user model, even if the default User model is sufficient for you. This model behaves identically to the default user model, but you’ll be able to customize it in the future if the need arises:

from django.contrib.auth.models import AbstractUser

class User(AbstractUser):
    pass

Don’t forget to point AUTH_USER_MODEL to it. Do this before creating any migrations or running manage.py migrate for the first time.

Also, register the model in the app’s admin.py:

from django.contrib import admin
from django.contrib.auth.admin import UserAdmin
from .models import User

admin.site.register(User, UserAdmin)

Changing to a custom user model mid-project

Changing AUTH_USER_MODEL after you’ve created database tables is significantly more difficult since it affects foreign keys and many-to-many relationships, for example.

This change can’t be done automatically and requires manually fixing your schema, moving your data from the old user table, and possibly manually reapplying some migrations. See #25313 for an outline of the steps.

Due to limitations of Django’s dynamic dependency feature for swappable models, the model referenced by AUTH_USER_MODEL must be created in the first migration of its app (usually called 0001_initial); otherwise, you’ll have dependency issues.

In addition, you may run into a CircularDependencyError when running your migrations as Django won’t be able to automatically break the dependency loop due to the dynamic dependency. If you see this error, you should break the loop by moving the models depended on by your user model into a second migration. (You can try making two normal models that have a ForeignKey to each other and seeing how makemigrations resolves that circular dependency if you want to see how it’s usually done.)

Reusable apps and AUTH_USER_MODEL

Reusable apps shouldn’t implement a custom user model. A project may use many apps, and two reusable apps that implemented a custom user model couldn’t be used together. If you need to store per user information in your app, use a ForeignKey or OneToOneField to settings.AUTH_USER_MODEL as described below.

Referencing the User model

If you reference User directly (for example, by referring to it in a foreign key), your code will not work in projects where the AUTH_USER_MODEL setting has been changed to a different user model.

get_user_model()

Instead of referring to User directly, you should reference the user model using django.contrib.auth.get_user_model(). This method will return the currently active user model – the custom user model if one is specified, or User otherwise.

When you define a foreign key or many-to-many relations to the user model, you should specify the custom model using the AUTH_USER_MODEL setting. For example:

from django.conf import settings
from django.db import models

class Article(models.Model):
    author = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
    )

When connecting to signals sent by the user model, you should specify the custom model using the AUTH_USER_MODEL setting. For example:

from django.conf import settings
from django.db.models.signals import post_save

def post_save_receiver(sender, instance, created, **kwargs):
    pass

post_save.connect(post_save_receiver, sender=settings.AUTH_USER_MODEL)

Generally speaking, it’s easiest to refer to the user model with the AUTH_USER_MODEL setting in code that’s executed at import time, however, it’s also possible to call get_user_model() while Django is importing models, so you could use models.ForeignKey(get_user_model(), ...).

If your app is tested with multiple user models, using @override_settings(AUTH_USER_MODEL=...) for example, and you cache the result of get_user_model() in a module-level variable, you may need to listen to the setting_changed signal to clear the cache. For example:

from django.apps import apps
from django.contrib.auth import get_user_model
from django.core.signals import setting_changed
from django.dispatch import receiver

@receiver(setting_changed)
def user_model_swapped(**kwargs):
    if kwargs['setting'] == 'AUTH_USER_MODEL':
        apps.clear_cache()
        from myapp import some_module
        some_module.UserModel = get_user_model()

Specifying a custom user model

When you start your project with a custom user model, stop to consider if this is the right choice for your project.

Keeping all user related information in one model removes the need for additional or more complex database queries to retrieve related models. On the other hand, it may be more suitable to store app-specific user information in a model that has a relation with your custom user model. That allows each app to specify its own user data requirements without potentially conflicting or breaking assumptions by other apps. It also means that you would keep your user model as simple as possible, focused on authentication, and following the minimum requirements Django expects custom user models to meet.

If you use the default authentication backend, then your model must have a single unique field that can be used for identification purposes. This can be a username, an email address, or any other unique attribute. A non-unique username field is allowed if you use a custom authentication backend that can support it.

The easiest way to construct a compliant custom user model is to inherit from AbstractBaseUser. AbstractBaseUser provides the core implementation of a user model, including hashed passwords and tokenized password resets. You must then provide some key implementation details:

class models.CustomUser

USERNAME_FIELD

A string describing the name of the field on the user model that is used as the unique identifier. This will usually be a username of some kind, but it can also be an email address, or any other unique identifier. The field must be unique (i.e., have unique=True set in its definition), unless you use a custom authentication backend that can support non-unique usernames.

In the following example, the field identifier is used as the identifying field:

class MyUser(AbstractBaseUser):
    identifier = models.CharField(max_length=40, unique=True)
    ...
    USERNAME_FIELD = 'identifier'

EMAIL_FIELD

A string describing the name of the email field on the User model. This value is returned by get_email_field_name().

REQUIRED_FIELDS

A list of the field names that will be prompted for when creating a user via the createsuperuser management command. The user will be prompted to supply a value for each of these fields. It must include any field for which blank is False or undefined and may include additional fields you want prompted for when a user is created interactively. REQUIRED_FIELDS has no effect in other parts of Django, like creating a user in the admin.

New in Django 3.0:

REQUIRED_FIELDS now supports ManyToManyFields without a custom through model. Since there is no way to pass model instances during the createsuperuser prompt, expect the user to enter IDs of existing instances of the class to which the model is related.

For example, here is the partial definition for a user model that defines two required fields - a date of birth and height:

class MyUser(AbstractBaseUser):
    ...
    date_of_birth = models.DateField()
    height = models.FloatField()
    ...
    REQUIRED_FIELDS = ['date_of_birth', 'height']

Note

REQUIRED_FIELDS must contain all required fields on your user model, but should not contain the USERNAME_FIELD or password as these fields will always be prompted for.

is_active

A boolean attribute that indicates whether the user is considered “active”. This attribute is provided as an attribute on AbstractBaseUser defaulting to True. How you choose to implement it will depend on the details of your chosen auth backends. See the documentation of the is_active attribute on the built-in user model for details.

get_full_name()

Optional. A longer formal identifier for the user such as their full name. If implemented, this appears alongside the username in an object’s history in django.contrib.admin.

get_short_name()

Optional. A short, informal identifier for the user such as their first name. If implemented, this replaces the username in the greeting to the user in the header of django.contrib.admin.

Importing AbstractBaseUser

AbstractBaseUser and BaseUserManager are importable from django.contrib.auth.base_user so that they can be imported without including django.contrib.auth in INSTALLED_APPS.

The following attributes and methods are available on any subclass of AbstractBaseUser:

class models.AbstractBaseUser

get_username()

Returns the value of the field nominated by USERNAME_FIELD.

clean()

Normalizes the username by calling normalize_username(). If you override this method, be sure to call super() to retain the normalization.

classmethod get_email_field_name()

Returns the name of the email field specified by the EMAIL_FIELD attribute. Defaults to 'email' if EMAIL_FIELD isn’t specified.

classmethod normalize_username(username)

Applies NFKC Unicode normalization to usernames so that visually identical characters with different Unicode code points are considered identical.

is_authenticated

Read-only attribute which is always True (as opposed to AnonymousUser.is_authenticated which is always False). This is a way to tell if the user has been authenticated. This does not imply any permissions and doesn’t check if the user is active or has a valid session. Even though normally you will check this attribute on request.user to find out whether it has been populated by the AuthenticationMiddleware (representing the currently logged-in user), you should know this attribute is True for any User instance.

is_anonymous

Read-only attribute which is always False. This is a way of differentiating User and AnonymousUser objects. Generally, you should prefer using is_authenticated to this attribute.

set_password(raw_password)

Sets the user’s password to the given raw string, taking care of the password hashing. Doesn’t save the AbstractBaseUser object.

When the raw_password is None, the password will be set to an unusable password, as if set_unusable_password() were used.

check_password(raw_password)

Returns True if the given raw string is the correct password for the user. (This takes care of the password hashing in making the comparison.)

set_unusable_password()

Marks the user as having no password set. This isn’t the same as having a blank string for a password. check_password() for this user will never return True. Doesn’t save the AbstractBaseUser object.

You may need this if authentication for your application takes place against an existing external source such as an LDAP directory.

has_usable_password()

Returns False if set_unusable_password() has been called for this user.

get_session_auth_hash()

Returns an HMAC of the password field. Used for Session invalidation on password change.

AbstractUser subclasses AbstractBaseUser:

class models.AbstractUser

clean()

Normalizes the email by calling BaseUserManager.normalize_email(). If you override this method, be sure to call super() to retain the normalization.

Writing a manager for a custom user model

You should also define a custom manager for your user model. If your user model defines username, email, is_staff, is_active, is_superuser, last_login, and date_joined fields the same as Django’s default user, you can install Django’s UserManager; however, if your user model defines different fields, you’ll need to define a custom manager that extends BaseUserManager providing two additional methods:

class models.CustomUserManager

create_user(username_field, password=None, **other_fields)

The prototype of create_user() should accept the username field, plus all required fields as arguments. For example, if your user model uses email as the username field, and has date_of_birth as a required field, then create_user should be defined as:

def create_user(self, email, date_of_birth, password=None):
    # create user here
    ...

create_superuser(username_field, password=None, **other_fields)

The prototype of create_superuser() should accept the username field, plus all required fields as arguments. For example, if your user model uses email as the username field, and has date_of_birth as a required field, then create_superuser should be defined as:

def create_superuser(self, email, date_of_birth, password=None):
    # create superuser here
    ...

For a ForeignKey in USERNAME_FIELD or REQUIRED_FIELDS, these methods receive the value of the to_field (the primary_key by default) of an existing instance.

BaseUserManager provides the following utility methods:

class models.BaseUserManager

classmethod normalize_email(email)

Normalizes email addresses by lowercasing the domain portion of the email address.

get_by_natural_key(username)

Retrieves a user instance using the contents of the field nominated by USERNAME_FIELD.

make_random_password(length=10, allowed_chars='abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789')

Returns a random password with the given length and given string of allowed characters. Note that the default value of allowed_chars doesn’t contain letters that can cause user confusion, including:

• i, l, I, and 1 (lowercase letter i, lowercase letter L, uppercase letter i, and the number one)
• o, O, and 0 (lowercase letter o, uppercase letter o, and zero)

Extending Django’s default User

If you’re entirely happy with Django’s User model, but you want to add some additional profile information, you could subclass django.contrib.auth.models.AbstractUser and add your custom profile fields, although we’d recommend a separate model as described in the “Model design considerations” note of Specifying a custom user model. AbstractUser provides the full implementation of the default User as an abstract model.

Custom users and the built-in auth forms

Django’s built-in forms and views make certain assumptions about the user model that they are working with.

The following forms are compatible with any subclass of AbstractBaseUser:

• AuthenticationForm: Uses the username field specified by USERNAME_FIELD.
• SetPasswordForm
• PasswordChangeForm
• AdminPasswordChangeForm

The following forms make assumptions about the user model and can be used as-is if those assumptions are met:

• PasswordResetForm: Assumes that the user model has a field that stores the user’s email address with the name returned by get_email_field_name() (email by default) that can be used to identify the user and a boolean field named is_active to prevent password resets for inactive users.

Finally, the following forms are tied to User and need to be rewritten or extended to work with a custom user model:

• UserCreationForm
• UserChangeForm

If your custom user model is a subclass of AbstractUser, then you can extend these forms in this manner:

from django.contrib.auth.forms import UserCreationForm
from myapp.models import CustomUser

class CustomUserCreationForm(UserCreationForm):

    class Meta(UserCreationForm.Meta):
        model = CustomUser
        fields = UserCreationForm.Meta.fields + ('custom_field',)

Custom users and django.contrib.admin

If you want your custom user model to also work with the admin, your user model must define some additional attributes and methods. These methods allow the admin to control access of the user to admin content:

class models.CustomUser

is_staff

Returns True if the user is allowed to have access to the admin site.

is_active

Returns True if the user account is currently active.

has_perm(perm, obj=None):

Returns True if the user has the named permission. If obj is provided, the permission needs to be checked against a specific object instance.

has_module_perms(app_label):

Returns True if the user has permission to access models in the given app.

You will also need to register your custom user model with the admin. If your custom user model extends django.contrib.auth.models.AbstractUser, you can use Django’s existing django.contrib.auth.admin.UserAdmin class. However, if your user model extends AbstractBaseUser, you’ll need to define a custom ModelAdmin class. It may be possible to subclass the default django.contrib.auth.admin.UserAdmin; however, you’ll need to override any of the definitions that refer to fields on django.contrib.auth.models.AbstractUser that aren’t on your custom user class.

from django.contrib.auth.admin import UserAdmin

class CustomUserAdmin(UserAdmin):
    ...
    fieldsets = UserAdmin.fieldsets + (
        (None, {'fields': ('custom_field',)}),
    )
    add_fieldsets = UserAdmin.add_fieldsets + (
        (None, {'fields': ('custom_field',)}),
    )

Custom users and permissions

To make it easy to include Django’s permission framework into your own user class, Django provides PermissionsMixin. This is an abstract model you can include in the class hierarchy for your user model, giving you all the methods and database fields necessary to support Django’s permission model.

PermissionsMixin provides the following methods and attributes:

class models.PermissionsMixin

is_superuser

Boolean. Designates that this user has all permissions without explicitly assigning them.

get_user_permissions(obj=None)

New in Django 3.0.

Returns a set of permission strings that the user has directly.

If obj is passed in, only returns the user permissions for this specific object.

get_group_permissions(obj=None)

Returns a set of permission strings that the user has, through their groups.

If obj is passed in, only returns the group permissions for this specific object.

get_all_permissions(obj=None)

Returns a set of permission strings that the user has, both through group and user permissions.

If obj is passed in, only returns the permissions for this specific object.

has_perm(perm, obj=None)

Returns True if the user has the specified permission, where perm is in the format "<app label>.<permission codename>" (see permissions). If User.is_active and is_superuser are both True, this method always returns True.

If obj is passed in, this method won’t check for a permission for the model, but for this specific object.

has_perms(perm_list, obj=None)

Returns True if the user has each of the specified permissions, where each perm is in the format "<app label>.<permission codename>". If User.is_active and is_superuser are both True, this method always returns True.

If obj is passed in, this method won’t check for permissions for the model, but for the specific object.

has_module_perms(package_name)

Returns True if the user has any permissions in the given package (the Django app label). If User.is_active and is_superuser are both True, this method always returns True.

Custom users and proxy models

One limitation of custom user models is that installing a custom user model will break any proxy model extending User. Proxy models must be based on a concrete base class; by defining a custom user model, you remove the ability of Django to reliably identify the base class.

If your project uses proxy models, you must either modify the proxy to extend the user model that’s in use in your project, or merge your proxy’s behavior into your User subclass.

A full example

Here is an example of an admin-compliant custom user app. This user model uses an email address as the username, and has a required date of birth; it provides no permission checking beyond an admin flag on the user account. This model would be compatible with all the built-in auth forms and views, except for the user creation forms. This example illustrates how most of the components work together, but is not intended to be copied directly into projects for production use.

This code would all live in a models.py file for a custom authentication app:

from django.db import models
from django.contrib.auth.models import (
    BaseUserManager, AbstractBaseUser
)


class MyUserManager(BaseUserManager):
    def create_user(self, email, date_of_birth, password=None):
        """
        Creates and saves a User with the given email, date of
        birth and password.
        """
        if not email:
            raise ValueError('Users must have an email address')

        user = self.model(
            email=self.normalize_email(email),
            date_of_birth=date_of_birth,
        )

        user.set_password(password)
        user.save(using=self._db)
        return user

    def create_superuser(self, email, date_of_birth, password=None):
        """
        Creates and saves a superuser with the given email, date of
        birth and password.
        """
        user = self.create_user(
            email,
            password=password,
            date_of_birth=date_of_birth,
        )
        user.is_admin = True
        user.save(using=self._db)
        return user


class MyUser(AbstractBaseUser):
    email = models.EmailField(
        verbose_name='email address',
        max_length=255,
        unique=True,
    )
    date_of_birth = models.DateField()
    is_active = models.BooleanField(default=True)
    is_admin = models.BooleanField(default=False)

    objects = MyUserManager()

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['date_of_birth']

    def __str__(self):
        return self.email

    def has_perm(self, perm, obj=None):
        "Does the user have a specific permission?"
        # Simplest possible answer: Yes, always
        return True

    def has_module_perms(self, app_label):
        "Does the user have permissions to view the app `app_label`?"
        # Simplest possible answer: Yes, always
        return True

    @property
    def is_staff(self):
        "Is the user a member of staff?"
        # Simplest possible answer: All admins are staff
        return self.is_admin

Then, to register this custom user model with Django’s admin, the following code would be required in the app’s admin.py file:

from django import forms
from django.contrib import admin
from django.contrib.auth.models import Group
from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
from django.contrib.auth.forms import ReadOnlyPasswordHashField

from customauth.models import MyUser


class UserCreationForm(forms.ModelForm):
    """A form for creating new users. Includes all the required
    fields, plus a repeated password."""
    password1 = forms.CharField(label='Password', widget=forms.PasswordInput)
    password2 = forms.CharField(label='Password confirmation', widget=forms.PasswordInput)

    class Meta:
        model = MyUser
        fields = ('email', 'date_of_birth')

    def clean_password2(self):
        # Check that the two password entries match
        password1 = self.cleaned_data.get("password1")
        password2 = self.cleaned_data.get("password2")
        if password1 and password2 and password1 != password2:
            raise forms.ValidationError("Passwords don't match")
        return password2

    def save(self, commit=True):
        # Save the provided password in hashed format
        user = super().save(commit=False)
        user.set_password(self.cleaned_data["password1"])
        if commit:
            user.save()
        return user


class UserChangeForm(forms.ModelForm):
    """A form for updating users. Includes all the fields on
    the user, but replaces the password field with admin's
    password hash display field.
    """
    password = ReadOnlyPasswordHashField()

    class Meta:
        model = MyUser
        fields = ('email', 'password', 'date_of_birth', 'is_active', 'is_admin')

    def clean_password(self):
        # Regardless of what the user provides, return the initial value.
        # This is done here, rather than on the field, because the
        # field does not have access to the initial value
        return self.initial["password"]


class UserAdmin(BaseUserAdmin):
    # The forms to add and change user instances
    form = UserChangeForm
    add_form = UserCreationForm

    # The fields to be used in displaying the User model.
    # These override the definitions on the base UserAdmin
    # that reference specific fields on auth.User.
    list_display = ('email', 'date_of_birth', 'is_admin')
    list_filter = ('is_admin',)
    fieldsets = (
        (None, {'fields': ('email', 'password')}),
        ('Personal info', {'fields': ('date_of_birth',)}),
        ('Permissions', {'fields': ('is_admin',)}),
    )
    # add_fieldsets is not a standard ModelAdmin attribute. UserAdmin
    # overrides get_fieldsets to use this attribute when creating a user.
    add_fieldsets = (
        (None, {
            'classes': ('wide',),
            'fields': ('email', 'date_of_birth', 'password1', 'password2'),
        }),
    )
    search_fields = ('email',)
    ordering = ('email',)
    filter_horizontal = ()


# Now register the new UserAdmin...
admin.site.register(MyUser, UserAdmin)
# ... and, since we're not using Django's built-in permissions,
# unregister the Group model from admin.
admin.site.unregister(Group)

Finally, specify the custom model as the default user model for your project using the AUTH_USER_MODEL setting in your settings.py:

AUTH_USER_MODEL = 'customauth.MyUser'