Squoosh.app is a PWA that compresses images for you in the browser. It supports many old and new image formats and processes them client-side in the browser through WebAssembly. This means your pictures stay safely on your own computer rather than being sent to a server somewhere, and that Squoosh works even when offline.
At Chrome DevSummit 2020 we announced Squoosh v2, together with the Squoosh CLI to bring all the codecs of Squoosh to the command-line using Node and WebAssembly. This allows you to compress entire folders with one command and make use of the CLI's to let it choose the codec parameters for you.
The CLI enables a lot of automation and so it's only natural that developers began asking for a more idiomatic interface than programmatically invoking the Squoosh CLI via the shell. Anton (@atjn on GitHub) stepped up to the task and separated the Squoosh CLI code into two parts: The command line interface code and the underlying core functionality.