When configuring Nginx with both HTTPS redirects and Let's Encrypt ACME challenges, the order of directives becomes critical. Here's the problematic configuration many developers encounter:

server {
    listen 80;
    server_name subdomain.example.com;

    return 301 https://$server_name$request_uri;  # This breaks renewal

    location /.well-known/acme-challenge {
        root /var/www/letsencrypt;
    }
}

Nginx processes location blocks in order, but the return 301 directive takes immediate precedence. This creates a catch-22 situation:

• Let's Encrypt needs HTTP access to verify domain ownership
• The redirect forces all HTTP traffic to HTTPS before the challenge can complete

Here's the correct way to structure your Nginx config:

server {
    listen 80;
    server_name subdomain.example.com;

    location /.well-known/acme-challenge {
        root /var/www/letsencrypt;
        allow all;
    }

    location / {
        return 301 https://$server_name$request_uri;
    }
}

For more complex setups, consider these patterns:

# Separate server block for ACME challenges
server {
    listen 80;
    server_name subdomain.example.com;
    location /.well-known/acme-challenge {
        root /var/www/letsencrypt;
    }
}

# Main server block for redirects
server {
    listen 80;
    server_name subdomain.example.com;
    return 301 https://$server_name$request_uri;
}

For zero-downtime renewals, add this to your certbot command:

sudo certbot renew --pre-hook "service nginx stop" --post-hook "service nginx start"

Or use webroot authentication method:

certbot certonly --webroot -w /var/www/letsencrypt -d example.com

Before running renewals, verify your setup with:

sudo nginx -t  # Test config syntax
sudo certbot renew --dry-run  # Test renewal process

When configuring Nginx for HTTPS redirection while maintaining Let's Encrypt certificate renewal capabilities, the order of directives becomes crucial. Many developers encounter this exact scenario:

server {
    listen 80;
    server_name subdomain.example.com;

    return 301 https://$server_name$request_uri;

    location /.well-known/acme-challenge {
        root /var/www/letsencrypt;
    }
}

The return 301 directive takes precedence over subsequent location blocks. When Let's Encrypt attempts to validate your domain by accessing http://subdomain.example.com/.well-known/acme-challenge/..., Nginx immediately redirects to HTTPS before processing the location block.

Always place the ACME challenge location block before any redirection directives:

server {
    listen 80;
    server_name subdomain.example.com;

    location /.well-known/acme-challenge {
        root /var/www/letsencrypt;
    }

    return 301 https://$server_name$request_uri;
}

For automated renewals, consider these approaches:

• Temporary disable redirect during renewal:

  # /etc/letsencrypt/renewal-hooks/pre/stop-nginx-redirect.sh
  sed -i 's/return 301/# return 301/' /etc/nginx/sites-enabled/your-site
  systemctl reload nginx

• Post-renewal re-enable:

  # /etc/letsencrypt/renewal-hooks/post/restore-nginx-redirect.sh
  sed -i 's/# return 301/return 301/' /etc/nginx/sites-enabled/your-site
  systemctl reload nginx

To test your configuration without waiting for renewal period:

sudo certbot renew --dry-run
# Or force renewal with
sudo certbot renew --force-renewal