Form Validation in Django

Last Updated : 10 Nov, 2025

Form validation ensures that user-submitted data meets specific requirements before being processed or saved. It can be applied to fields such as username, gender, or text inputs to maintain accuracy and consistency. Django simplifies this process by combining form handling and validation logic within its form classes.

Example: Custom Validation with Django Forms

Consider a project named 'geeksforgeeks' having an app named 'geeks.

Step 1: Create the Model

In geeks/models.py, define a model named Post to store user data:

Python

from django.db import models

class Post(models.Model):
    MALE = 'M'
    FEMALE = 'F'
    GENDER_CHOICES = [
        (MALE, 'Male'),
        (FEMALE, 'Female'),
    ]

    username = models.CharField(max_length=20, blank=False, null=False)
    text = models.TextField(blank=False, null=False)
    gender = models.CharField(max_length=6, choices=GENDER_CHOICES, default=MALE)
    time = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return self.username

Step 2: Apply Migrations

After creating this model, two commands need to be run to create the corresponding database tables:

python manage.py makemigrations
python manage.py migrate

Step 3: Create a ModelForm with Validation

Creating a form involves defining validation rules for fields, such as requiring the username to be at least 5 characters and the post text to be at least 10 characters. These rules are implemented in the PostForm class.

In geeks/forms.py, define a form that includes custom validation logic:

Python

from django import forms
from django.forms import ModelForm
from .models import Post

class PostForm(ModelForm):
    class Meta:
        model = Post
        fields = ["username", "gender", "text"]

    def clean(self):
        cleaned_data = super().clean()
        username = cleaned_data.get('username')
        text = cleaned_data.get('text')

        # Validate username and text length
        if username and len(username) < 5:
            self.add_error('username', 'Minimum 5 characters required.')

        if text and len(text) < 10:
            self.add_error('text', 'Post should contain at least 10 characters.')

        return cleaned_data

Step 4: Define the View

In geeks/views.py, create a view to handle GET and POST requests.

Python

from django.shortcuts import render, HttpResponse
from .forms import PostForm

def home(request):
    if request.method == 'POST':
        form = PostForm(request.POST)
        if form.is_valid():
            form.save()
            return HttpResponse("Data submitted successfully.")
        return render(request, 'home.html', {'form': form})
    
    form = PostForm()
    return render(request, 'home.html', {'form': form})

Step 5: Configure URLs

In geeks/urls.py, map the root URL to the home view.

Python

from django.urls import path
from . import views

urlpatterns = [
    path('', views.home, name='home'),
]

Include app’s URLs in the project-level geeksforgeeks/urls.py:

Python

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('geeks.urls')),
]

Step 6: Create the Template

In geeks/templates/home.html, design a simple form using Bootstrap for styling.

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Django Form Validation</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
</head>
<body style="padding-top: 60px; background-color: #f5f7f8;">
    <div class="container">
        <div class="row">
            <div class="col-md-4 col-md-offset-4">
                <h2>Post Form</h2>
                <form method="POST">
                    {% csrf_token %}
                    {{ form.as_p }}
                    <button type="submit" class="btn btn-primary">Submit</button>
                </form>
            </div>
        </div>
    </div>
</body>
</html>

Step 7: Run the Server

python manage.py runserver

Visit: http://127.0.0.1:8000/ to view the form in action

If the form is submitted with a username shorter than 5 characters or post text shorter than 10 characters, validation errors are displayed immediately. The form highlights the invalid fields and shows appropriate error messages.