When a user drops forty product photos onto an upload page, decoding and resizing all of them at the same moment can freeze the tab and spike memory. Processing them one by one is safe but slow. A bounded concurrency queue sits between those extremes: a fixed number of images are processed at a time, every file gets its own success or failure result, and the user can cancel the remaining work.

This tutorial builds that queue in TypeScript and pairs it with a real thumbnail task that uses createImageBitmap and OffscreenCanvas . The two parts are separate on purpose.…