Chrome extension

Chrome extensions are small, powerful software modules: they customize the browser experience, inject new features, and interact with web content using standard web technologies and dedicated Chrome APIs.

A Chrome extension is a focused application built with HTML, CSS, and JavaScript that directly enhances the Google Chrome browser's functionality. It operates via a declarative `manifest.json` file (Manifest V3 is current) which defines its permissions and resources. Extensions execute code in dedicated background service workers, modify web pages via content scripts, or provide user interfaces through toolbar actions and side panels. For example, an extension can block ads using the `declarativeNetRequest` API, manage tabs, or integrate third-party productivity tools directly into the browser interface.

https://developer.chrome.com/docs/extensions