Fix SSL "Self-Signed Certificate" Error

Understanding the Error

Self-signed certificates are not trusted by browsers for public websites.

Fix for Public Websites

Don't use self-signed certs on production. Get free certificate:

sudo apt install certbot python3-certbot-nginx -y
sudo certbot --nginx -d yourdomain.com

Fix for Internal/Development Use

If you must use self-signed for testing:

Option 1: Browser Exception

Click "Advanced" → "Proceed to site" (not for production).

Option 2: Add to Trust Store (Local Machine)

# Linux
sudo cp certificate.crt /usr/local/share/ca-certificates/
sudo update-ca-certificates

# Windows
Import .crt file to "Trusted Root Certification Authorities"

Generate Proper Self-Signed Cert (for internal use)

openssl req -x509 -nodes -days 365 -newkey rsa:2048 
    -keyout selfsigned.key -out selfsigned.crt 
    -subj "/CN=yourdomain.com"

Create Your Own CA (for multiple internal sites)

# Generate CA
openssl genrsa -out myCA.key 2048
openssl req -x509 -new -nodes -key myCA.key -sha256 -days 3650 -out myCA.pem

# Sign certs with your CA
# Then trust myCA.pem on all internal machines