[mikea1]

You can quickly go offline via dev tools. In Chrome, it's very simple[0].

[0] https://developer.chrome.com/docs/devtools/network/reference...

[pritambaral]

Workaround:

1. Install ServiceWorker.

2. Save data to LocalStorage/IndexedDB/ServiceWorker Cache/ServiceWorker Memory.

3. Wait for devtools to be closed, enabling internet access, send data from ServiceWorker.

[Zuiii]

I'd create a fresh browser profile just for this, download it, then point it to use a http/socks proxy that will never exist.

Work around that.