Shared Web Workers are a relatively new feature that allow multiple scripts communicate with a single worker. A good use case would be for example sharing computation between multiple browser tabs.

When it comes to browser support, the feature is well supported apart from Safari. It used to have the feature for a while but then it was dropped. The background for the decision is explained at https://bugs.webkit.org/show_bug.cgi?id=149850 .

As we would have a direct use case for the feature in our current project, would it be possible for you to consider inclusion of the feature to threads.js? I am happy to contribute the code if we can agree on the steps. I imagine we would have to expose SharedWorker from threads.js itself and then also make sure the addition works with the webpack plugin. Safari might require some kind of a strategy as well.

Reference: GoogleChromeLabs/worker-plugin#42 (shared worker support in Google's worker-plugin)