Custom Field Validations in Django Models

Last Updated : 14 May, 2025

In Django, field validation is the process of ensuring that the data entered into a field meets certain criteria. Custom field validation allows us to enforce rules such as checking for specific formats, length restrictions or even more complex conditions, like validating an email to belong to a specific domain.

Validation in django can be done at the model level, meaning that it is executed automatically whenever we create or update an instance of a model. This ensures data integrity without needing to add extra validation logic elsewhere in your code.

Syntax for Custom Validators

field_name = models.Field(validators = [function 1, function 2])

validators is a list of validator functions that will be executed when the field value is set.
Each validator function accepts a single argument, value, which is the data entered for the field.

Django Custom Field Validation Example

Illustration of validators using an example. Consider a project named geeksforgeeks having an app named geeks.

Refer to the following articles to check how to create a project and an app in Django.
How to Create a Basic Project using MVT in Django?
How to Create an App in Django ?

Step 1: Define the Model

First, let's define a basic model with a CharField for the email address:

Python

from django.db import models from django.db.models import Model  class GeeksModel(Model):     geeks_mail = models.CharField(max_length = 200)

Step 2: Create a Validator Function

Now, let’s create a custom validator function that will check whether the email address ends with @gmail.com. If it doesn't, the function will raise a ValidationError.

Python

from django.db import models from django.core.exceptions import ValidationError  # creating a validator function def validate_geeks_mail(value):     if "@gmail.com" in value:         return value     else:         raise ValidationError("This field accepts mail id of google only")

Step 3: Attach the Validator to the Model Field

Next, we attach this validator function to the geeks_mail field in our model using the validators parameter:

Python

from django.db import models from django.core.exceptions import ValidationError  # creating a validator function def validate_geeks_mail(value):     if "@gmail.com" in value:         return value     else:         raise ValidationError("This field accepts mail id of google only")   # Create your models here. class GeeksModel(models.Model):     geeks_mail = models.CharField(max_length = 200, validators =[validate_geeks_mail])

Now, the geeks_mail field will only accept email addresses containing @gmail.com. Any other email address will trigger a ValidationError. Let us try to create an instance without gmail.com and check if our validation worked or not. Note that after every change in models.py one needs to run makemigrations and migrate commands.

In your browser go to http://localhost:8000/admin/geeks/geeksmodel/add/ and enter "[email protected]".

Let us check if it gets saved in database.

custom-field-validations-django-models — Custom Validation

So the validation worked and this field can only accept email ids ending with @gmail.com. This way one can apply any kind of custom validation on value.

Meta Class in Models - Django

NaveenArora

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Custom Field Validations in Django Models

Syntax for Custom Validators

Django Custom Field Validation Example

Step 1: Define the Model

Step 2: Create a Validator Function

Step 3: Attach the Validator to the Model Field

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