Is NodeBox really compiled by a local browser without the need for a network?

[gitfei1231]

I want to ask a question, the documentation says that it runs completely in the browser, even if you don't need an Internet, but the links generated by the iframe after I run it are all official links

https:vu13f7e-3000.nodebox.codesandbox.io
https:nodebox-runtime.codesandbox.io

How could this link work without an Internet connection?

[DeMoorJasper]

All compilation and execution happens locally in the browser, but we still need to use some domain names to actually host nodebox.

These unique domains are for running the service worker proxies that forward the http requests from the iframe to the nodebox instance