Make User email unique django

There is a great example of this in Django's docs - https://docs.djangoproject.com/en/2.1/topics/auth/customizing/#a-full-example.

You have to declare the email field in your AbstractBaseUser model as unique=True.

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)

Here is a working code

Use the below code snippets in any of your models.py

models.py

from django.contrib.auth.models import User
User._meta.get_field('email')._unique = True

django version : 3.0.2

Reference : Django auth.user with unique email

The best answer is to use CustomUser by subclassing the AbstractUser and put the unique email address there. For example:

from django.contrib.auth.models import AbstractUser


class CustomUser(AbstractUser):
    email = models.EmailField(unique=True)

and update the settings with AUTH_USER_MODEL="app.CustomUser".

But if its not necessary for you to store the unique email in Database or maybe not use it as username field, then you can update the form's clean method to put a validation. For example:

from django.core.exceptions import ValidationError


class YourForm(UserCreationForm):

    def clean(self):
       email = self.cleaned_data.get('email')
       if User.objects.filter(email=email).exists():
            raise ValidationError("Email exists")
       return self.cleaned_data

Update

If you are in mid project, then you can follow the documentation on how to change migration, in short which is to:

1. Backup you DB
2. Create a custom user model identical to auth.User, call it User (so many-to-many tables keep the same name) and set db_table='auth_user' (so it uses the same table)
3. Delete all Migrations File(except for __init__.py)
4. Delete all entry from table django_migrations
5. Create all migrations file using python manage.py makemigrations
6. Run fake migrations by python manage.py migrate --fake
7. Unset db_table, make other changes to the custom model, generate migrations, apply them

But if you are just starting, then delete the DB and migrations files in migration directory except for __init__.py. Then create a new DB, create new set of migrations by python manage.py makemigrations and apply migrations by python manage.py migrate.

And for references in other models, you can reference them to settings.AUTH_USER_MODEL to avoid any future problems. For example:

user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.DO_NOTHING)

It will automatically reference to the current User Model.