Forbidden (403) CSRF verification failed. Request aborted. Even using the {% csrf_token %}

Resolving Django's 'CSRF verification failed' Error with {% csrf_token %}

Understand why you're encountering the 'Forbidden (403) CSRF verification failed' error in Django, even when using {% csrf_token %}, and learn effective strategies to diagnose and fix it.

The 'Forbidden (403) CSRF verification failed. Request aborted.' error is a common hurdle for Django developers. While Django's built-in Cross-Site Request Forgery (CSRF) protection is robust and essential for security, encountering this error even after correctly placing {% csrf_token %} in your forms can be frustrating. This article will delve into the common causes behind this persistent issue and provide a systematic approach to troubleshooting and resolving it.

Understanding Django's CSRF Protection

Django's CSRF protection works by ensuring that all POST requests originating from your site include a secret token. This token is generated by Django and embedded in the form. When the form is submitted, Django verifies that the submitted token matches the one stored in the user's session. If they don't match, or if the token is missing, the request is rejected with a 403 Forbidden error. This mechanism prevents malicious websites from tricking authenticated users into performing unwanted actions on your site.

sequenceDiagram
    actor User
    participant Browser
    participant DjangoServer

    User->>Browser: Requests form page
    Browser->>DjangoServer: GET /my-form/
    DjangoServer-->>Browser: Renders form with {% csrf_token %}
    Browser->>User: Displays form

    User->>Browser: Fills form, clicks submit
    Browser->>DjangoServer: POST /my-form/ (includes CSRF token)
    DjangoServer->>DjangoServer: Verifies CSRF token
    alt Token Valid
        DjangoServer-->>Browser: Processes request (200 OK)
    else Token Invalid/Missing
        DjangoServer-->>Browser: Returns 403 Forbidden (CSRF Failed)
    end

Django CSRF Protection Flow

Common Causes for CSRF Verification Failure

Even with {% csrf_token %} in place, several factors can lead to CSRF verification failure. Understanding these common pitfalls is key to effective debugging.

1. Missing or Incorrect {% csrf_token %} Placement

While you might think you've included it, double-check its placement. It must be inside the <form> tags of any form that uses the POST method. If you're building forms dynamically with JavaScript, ensure the token is correctly injected.

<form method="post" action="/submit-data/">
    {% csrf_token %}
    <input type="text" name="my_field">
    <button type="submit">Submit</button>
</form>

Correct placement of {% csrf_token %} within a Django form.

2. Session/Cookie Issues

Django's CSRF protection relies heavily on session cookies. If these cookies aren't being set or are being blocked, the CSRF token cannot be validated. Common scenarios include:

• Browser Blocking Cookies: Users might have browser settings that block third-party cookies, or even all cookies.
• Incorrect CSRF_COOKIE_DOMAIN or CSRF_COOKIE_SECURE: If you've customized these settings in settings.py, ensure they are correct for your deployment environment. CSRF_COOKIE_DOMAIN should match your domain (e.g., .example.com), and CSRF_COOKIE_SECURE should be True if you're serving over HTTPS.
• Proxy/Load Balancer Configuration: If your Django app is behind a proxy or load balancer, it might be stripping or modifying headers, preventing cookies from being set or read correctly. Ensure X-Forwarded-Proto is correctly configured if using HTTPS behind a proxy.

# In settings.py

# Example for production (replace with your actual domain)
CSRF_COOKIE_DOMAIN = '.yourdomain.com'

# Set to True in production if using HTTPS
CSRF_COOKIE_SECURE = True

# Ensure session cookies are also secure if using HTTPS
SESSION_COOKIE_SECURE = True

# If using a proxy that sets X-Forwarded-Proto
USE_X_FORWARDED_HOST = True
SECURE_PROXY_SSL_HEADER = ('HTTP_X_FORWARDED_PROTO', 'https')

Example Django settings for CSRF and session cookies in a production environment.

3. Caching Issues

Aggressive caching, especially at the browser or server level, can serve stale HTML pages without a fresh CSRF token. If a user loads a cached page, then submits a form, the token might be expired or invalid. Ensure that pages containing forms are not aggressively cached or that your caching strategy properly handles dynamic content like CSRF tokens.

4. Asynchronous (AJAX) Requests

When making AJAX POST requests, you cannot rely on {% csrf_token %} directly in your JavaScript. You need to manually retrieve the CSRF token and include it in your request headers or as part of the form data. Django expects the token in either the X-CSRFToken header or as a form field named csrfmiddlewaretoken.

// Function to get CSRF token from cookie
function getCookie(name) {
    let cookieValue = null;
    if (document.cookie && document.cookie !== '') {
        const cookies = document.cookie.split(';');
        for (let i = 0; i < cookies.length; i++) {
            const cookie = cookies[i].trim();
            // Does this cookie string begin with the name we want?
            if (cookie.substring(0, name.length + 1) === (name + '=')) {
                cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
                break;
            }
        }
    }
    return cookieValue;
}

// Example AJAX POST request using Fetch API
fetch('/api/submit-data/', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json',
        'X-CSRFToken': getCookie('csrftoken') // Get token from cookie
    },
    body: JSON.stringify({ key: 'value' })
})
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.error('Error:', error));

Handling CSRF tokens in JavaScript for AJAX requests.

5. CSRF_TRUSTED_ORIGINS Configuration

If your Django application is served from a different domain or subdomain than where your forms are being submitted from (e.g., an API on api.example.com and a frontend on app.example.com), you might need to configure CSRF_TRUSTED_ORIGINS in your settings.py. This setting specifies a list of trusted origins for cross-site POST requests.

# In settings.py

CSRF_TRUSTED_ORIGINS = [
    'https://*.yourfrontend.com',
    'https://yourdomain.com',
    'http://localhost:3000' # For local development
]

Configuring CSRF_TRUSTED_ORIGINS for cross-domain requests.

6. Decorator/Middleware Order

Ensure that Django's CsrfViewMiddleware is correctly placed in your MIDDLEWARE setting in settings.py. It should typically come before any view middleware that might short-circuit the request or perform actions that prevent the CSRF token from being processed.

# In settings.py

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware', # This should be here
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

Standard MIDDLEWARE configuration showing CsrfViewMiddleware placement.

Troubleshooting Steps

Follow these steps to systematically diagnose and resolve CSRF issues:

1. Verify {% csrf_token %} in HTML Source

After rendering the page, view the page source (Ctrl+U or Cmd+Option+U). Search for csrfmiddlewaretoken. Ensure it's present within your <form> tag and has a valid value (a long string of characters).

2. Check Browser Cookies

In your browser's developer tools (Application tab -> Cookies), check if a cookie named csrftoken is present for your domain. If not, investigate your settings.py for CSRF_COOKIE_DOMAIN, CSRF_COOKIE_SECURE, and SESSION_COOKIE_SECURE.

3. Inspect Network Requests

When submitting the form, go to the Network tab in developer tools. Click on the POST request that failed. Look at the 'Headers' tab to see if the csrftoken is being sent (either in the form data or as an X-CSRFToken header for AJAX). Check the 'Response' tab for detailed error messages.

4. Review Django Logs

Check your Django server logs for any related errors or warnings. Sometimes, more detailed information about why the CSRF check failed can be found there.

5. Test with CSRF_FAILURE_VIEW

For more detailed debugging, you can temporarily set CSRF_FAILURE_VIEW in settings.py to a custom view that logs the request details. This allows you to inspect the request that failed the CSRF check.

By systematically checking these areas, you should be able to pinpoint the exact cause of your 'CSRF verification failed' error and restore the security and functionality of your Django application.