How do offline VK clients work?

Question

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Lately I've been seeing a variety of new clients. Which allow you to sit in VK, while the status of the account on the online does not change.
Example:
https://chrome.google.com/webstore/detail/vk-inviz...
There are also similar applications for ios.
I would like to know how such clients manage to receive data from the VK API while leaving the user offline.

Answer 1

They work with the VK Api without calling the account.setOnline method, which is called automatically when you enter VK or go to the user's page.
UPD on the extension:
This is some kind of nonsense :)
The extension simply edits the source code of the page, removing "online" just for you.