Authentication Backends

Authentication backends control how users authenticate. The default backend checks username/password against the database. You can create custom backends to authenticate via email, LDAP, OAuth, or any custom method.

15 min•By Priygop Team•Updated 2026

Backend Concepts

ModelBackend - Default, authenticates with username + password
Custom backends subclass BaseBackend
authenticate(request, **credentials) - Verify credentials
get_user(user_id) - Retrieve user by ID
AUTHENTICATION_BACKENDS setting - list of backend classes
Django tries each backend in order until one succeeds
Common custom: login with email instead of username

Email Auth Backend

# accounts/backends.py
# from django.contrib.auth.backends import ModelBackend
# from django.contrib.auth import get_user_model

# User = get_user_model()

# class EmailBackend(ModelBackend):
#     """Allow login with email instead of username"""
#     def authenticate(self, request, username=None, password=None, **kwargs):
#         try:
#             # Try email first
#             user = User.objects.get(email=username)
#         except User.DoesNotExist:
#             try:
#                 # Fallback to username
#                 user = User.objects.get(username=username)
#             except User.DoesNotExist:
#                 return None
#
#         if user.check_password(password) and self.user_can_authenticate(user):
#             return user
#         return None

# settings.py
# AUTHENTICATION_BACKENDS = [
#     'accounts.backends.EmailBackend',
# ]

# Now users can login with email OR username
# authenticate(request, username='alice@example.com', password='pass')
# authenticate(request, username='alice', password='pass')

?? Tip

Tip

Create custom authentication backends for social login, LDAP, or API-based auth. Register them in AUTHENTICATION_BACKENDS.

Diagram

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QuerySets are LAZY - no DB hit until evaluated.

?? Common Mistake

Warning

Not handling failed authentication gracefully. Always check if authenticate() returns None and show a clear error.

?? Practice Task

Note

(1) Create a custom auth backend. (2) Support email-based login. (3) Register it in AUTHENTICATION_BACKENDS.

Quick Quiz

Key Takeaways

Authentication backends control how users authenticate.
ModelBackend - Default, authenticates with username + password
Custom backends subclass BaseBackend
authenticate(request, **credentials) - Verify credentials

Topics in This Module

Backend Concepts

ModelBackend - Default, authenticates with username + password

Custom backends subclass BaseBackend

authenticate(request, **credentials) - Verify credentials

get_user(user_id) - Retrieve user by ID

AUTHENTICATION_BACKENDS setting - list of backend classes

Django tries each backend in order until one succeeds

Common custom: login with email instead of username

Email Auth Backend

# accounts/backends.py
# from django.contrib.auth.backends import ModelBackend
# from django.contrib.auth import get_user_model

# User = get_user_model()

# class EmailBackend(ModelBackend):
#     """Allow login with email instead of username"""
#     def authenticate(self, request, username=None, password=None, **kwargs):
#         try:
#             # Try email first
#             user = User.objects.get(email=username)
#         except User.DoesNotExist:
#             try:
#                 # Fallback to username
#                 user = User.objects.get(username=username)
#             except User.DoesNotExist:
#                 return None
#
#         if user.check_password(password) and self.user_can_authenticate(user):
#             return user
#         return None

# settings.py
# AUTHENTICATION_BACKENDS = [
#     'accounts.backends.EmailBackend',
# ]

# Now users can login with email OR username
# authenticate(request, username='alice@example.com', password='pass')
# authenticate(request, username='alice', password='pass')

Topics in This Module