browser extension; web browser extension
Computing term for a small software module that adds functionality to a web browser. Often used in the full form ブラウザ拡張機能.
See also: ブラウザ拡張機能
Installing this browser extension allows you to block ads.
I manage passwords with a browser extension.
Compound of ブラウザ (browser) and 拡張 (extension, expansion). A modern technical term.