Enforce user to turn browser into OFFLINE mode

[gwpl]

Could you Enforce user to turn either browser (in developer tools) or computer into offline mode ?

Like Banana Split ( https://bs.parity.io/ <=> https://github.com/paritytech/banana_split ) is doing, which when (run locally after downloading .html file) displays message :

Please go offline, so your secrets won't leak accidentally

This application doesn't require Internet access, and you shouldn't be using it from a brower which has one.

It's really trivial to accidentally upload your unencrypted secrets somewhere, with a help of your browser spellchecker, webpage translation extension and such.

In Firefox, please go to Menu→More→Work Offline.

In Chrome, you'll have to open DevTools (Ctrl+Shift+I), then in the Network tab there check the "Offline" checkbox. (DON'T CLOSE DEVELOPER TOOLS AFTER THAT!) 

[nkcmr]

How about a nice warning instead? It disappears when the user either shuts off page access with DevTools, actually physically disconnects their computer from the network, or hits the "Dismiss" button.

Forcing a user to do so seems a tad heavy-handed.

[gwpl]

It depends on judgement. Some people will not do security measure unless they have to. Fortunately here user does not have to turn off internet connectivity to whole computer, but can temporarily turn it off in a browser. But, again, depends on your judgement, warning is absolutely great improvement to overall situation and design! Thank you for care and hard work!