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.
LaunchDarkly is a continuous delivery and feature flags as a service platform that integrates into a company's current development cycle.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.