Install Let’s Encrypt SSL on Nginx for Django/Flask

Running Python frameworks such as Django or Flask behind Nginx demands more than a basic configuration. Users expect HTTPS, browsers enforce TLS 1.2+, and search engines reward those who serve secure traffic. Free certificates from Let’s Encrypt make this achievable. If you’d prefer a fully managed environment including Nginx tuning and SSL monitoring, check out our **Linux Server Management** service.

Before You Begin - Requirements

A registered domain pointing via A + www records to your server
An Nginx server block in /etc/nginx/sites-available/your-domain.conf
A working Python application using Django or Flask
SSH root or sudo access
Ensured ports 80/443 open on your firewall

If you have a high-traffic application and want performance tuning included, see our **Server Optimization Service** .

Step 1: Install Certbot for Let’s Encrypt

Update your repositories:

sudo apt-get update

Install Certbot and the Nginx plugin (modern method):

sudo apt-get install -y certbot python3-certbot-nginx

Clone method (not recommended for 2025):

sudo git clone https://github.com/certbot/certbot /opt/letsencrypt

Step 2: Confirm Nginx Configuration

Open your server block and verify:

sudo nano /etc/nginx/sites-available/iserversupport.com

Check the server_name directive:

server_name iserversupport.com www.iserversupport.com;

Validate Nginx and reload:

sudo nginx -t
sudo systemctl reload nginx

Step 3: Obtain the SSL Certificate

Run:

sudo certbot --nginx -d iserversupport.com -d www.iserversupport.com

If IPv6 records exist and fail, remove AAAA records temporarily.

The interactive plugin will configure Nginx and reload automatically.

Step 4: Configure Django / Flask for HTTPS

Django:

In settings.py :

SECURE_SSL_REDIRECT = True
SESSION_COOKIE_SECURE = True
CSRF_COOKIE_SECURE = True

Flask:

app.config.update({
'SESSION_COOKIE_SECURE': True,
'PREFERRED_URL_SCHEME': 'https'
})

Update your Nginx proxy block:

proxy_set_header X-Forwarded-Proto $scheme;

Step 5: Set Up Auto-Renewal

Let’s Encrypt certificates last 90 days. The package adds a cron job:

Test renewal manually:

sudo certbot renew --dry-run

No errors? You’re good.

For monitoring, consider turning to our **Server Security Service** .

Troubleshooting Common Problems

Symptom	Cause	Fix
SSL fails, browser shows Connection refused	Port 443 blocked	Open port in firewall
DNS still shows HTTP	server_name mismatch	Confirm server block matches domain
Large app bundle fails	Python dependencies	Optimize with caching & CDN
Renewal fails	Certbot error	Verify cron job & DNS records

Conclusion

Securing Django or Flask with Let’s Encrypt on Nginx is straightforward when you follow the correct steps - from installing Certbot to enforcing HTTPS in your settings. While this guide covers the essentials, we can manage full-stack tuning and SSL maintenance for you through our **Linux Server Management** or **Server Optimization Service** .

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