cdnjs is a free distributed JS library delivery service.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
JSDelivr is a free public CDN for open-source projects. It can serve web files directly from the npm registry and GitHub repositories without any configuration.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.
Unpkg is a content delivery network for everything on npm.
Vercel is a cloud platform for static frontends and serverless functions.