cdnjs is a free distributed JS library delivery service.
Google Analytics is a free web analytics service that tracks and reports website traffic.
Google Sign-In is a secure authentication system that reduces the burden of login for users, by enabling them to sign in with their Google account.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Vercel is a cloud platform for static frontends and serverless functions.