Hands-on guide to securing a Flask app with HTTPS using Let's Encrypt: why SSL matters (security, trust, SEO), certificate types (DV/OV/EV), installing Certbot, obtaining certs via webroot, locating them under /etc/letsencrypt/live, copying fullchain.pem/privkey.pem into the app, enabling HTTPS/redirects with flask-sslify, updating WSGI, and running on port 443 with ssl_context.
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