How to fix "ERR_CONNECTION_REFUSED"

This site can't be reached
example.com refused to connect.
ERR_CONNECTION_REFUSED

Common causes

• Nginx, Apache or the Node/dev server is stopped or failed to start
• The app listens on a different port, or only on 127.0.0.1 instead of 0.0.0.0
• No HTTPS listener on port 443 while the browser forces HTTPS
• A firewall actively rejects the port (ufw, firewalld, cloud security group)
• DNS points the domain at the wrong server IP
• A local proxy or VPN setting in the browser

How to fix it

1. Check the service is running. Run sudo systemctl status nginx (or apache2). If it failed, run sudo nginx -t to find config errors, fix them, then start it with sudo systemctl start nginx.
2. See what is listening. Run sudo ss -tlnp | grep -E ':80|:443'. If nothing is on 443, HTTPS is not configured; if the app shows 127.0.0.1:3000, it only accepts local connections.
3. Open the firewall. Allow web traffic with sudo ufw allow 'Nginx Full' or sudo firewall-cmd --permanent --add-service=https && sudo firewall-cmd --reload. On cloud servers also check the security group.
4. Verify DNS. Run dig +short example.com and compare it to your server's IP. Update the A record if it points somewhere else.
5. Fix local dev servers. For localhost errors, start the dev server again and use the exact port it prints. In Docker, publish the port with -p 3000:3000 and bind the app to 0.0.0.0.
6. Rule out browser proxy settings. Try another browser or curl -v http://example.com. If curl works, check the browser's proxy or VPN extension.

Check listeners and the web server status

sudo ss -tlnp | grep -E ':(80|443)\b'
sudo systemctl status nginx --no-pager
sudo nginx -t && sudo systemctl restart nginx

How to stop it happening again

• Enable web services at boot with systemctl enable
• Test config before restarting services
• Monitor uptime from an outside location
• Document which ports each app uses