Web Workers API - Web APIs (opens in new tab)

Problem Statement Web Workers let you run JavaScript in the background, on a separate thread, so your main page stays responsive. Have you ever clicked a button on a web app and watched the whole page freeze while some heavy logic runs? Or felt that annoying lag while a large dataset gets processed? That frozen feeling happens because JavaScript normally runs everything—UI updates, click handlers, data crunching—on a single thread. Web Workers fix this by handing off the heavy lifting to a ba...