Obs.js: context-aware web performance for everyone

Obs.js is a tiny JavaScript library that provides context-aware signals about your user's environment.

It uses the Navigator and Battery APIs to add CSS classes and a JS object you can use to adapt your site's performance.

Key features:

• Detects slow connections and low battery.
• Infers device capability (RAM/CPU).
• Provides simple CSS classes (.has-battery-low) and a JS object (window.obs).
• No dependencies, just a single inline script.

It's a smart way to conditionally load assets or disable heavy features for users who need a lighter experience.

👉 Blog Post

👉 GitHub Repo

👉 Live Demo