Understanding Browser Permissions and Features

Modern browsers expose numerous powerful APIs that can access sensitive device capabilities: geolocation, camera, microphone, accelerometer, payment handlers, and more. Without proper controls, these features can be exploited by malicious scripts or compromised third-party content. Permissions-Policy creates a declarative security layer that restricts feature access at the HTTP header level, preventing unauthorized use even if malicious code executes.

The security implications extend beyond obvious privacy concerns. Features like document.write(), synchronous XHR, and unoptimized images can degrade performance, while APIs like ambient light sensors or battery status can be used for fingerprinting. By controlling these features, you protect both security and performance.