OBS.JS

Summary from the TLDR Web Dev newsletter

Obs.js is a JavaScript library that improves web performance by adapting websites to users' network conditions and battery status. It uses the Navigator and Battery APIs to gather contextual information, adding CSS classes to the `html` element and exposing data via the `window.obs` object. This allows developers to conditionally load assets or disable features based on the user's environment, optimizing the experience for both high and low-resource devices.