Language Reactor is a browser extension that helps users learn new vocabulary by using active recall and spaced repetition while they browse webpages. Users click on unfamiliar words or listen to dialogues, then attempt to recall the meaning before seeing the translation, with the app providing hints as they improve. The extension integrates with text and audio on various sites, allowing learning in context without leaving the page. Customizable difficulty settings let learners tailor the experience to their needs.