> Service workers are like adding extra threads when running JS in your browser. People use them in client-side web app code to get around the single-threadedmess of JavaScript. [...]

Aren't you just describing workers in general here (without the "service" part)?

To me "Service Workers" is a worker purposed especially for proxyfying requests made by the client, on the client, and act upon it (example: by returning a version cached by the js). The main use-case I've seen is implementing an offline mode.

When you just want to unlock multi-threading capabilities in JavaScript, you just rely on "WebWorkers" another worker mechanism without the proxy part, I've never seen those referred as "Service Workers".

With that written, I don't get what Service Workers have to do being on the server-side though :/