How to get HTML from browser inside java app without url?

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Java

it is not hard to get html from url to java app by jsoup or something but here the problem is the website that the app is going to parse html from, is an online chess game (https://www.playok.com/en/chess/) which has thousands of webpages which they get changed constantly, plus it needs cookies acception and login.

so probably the only way that remains is to get the html from the browser and not from the url; is there any library or a method that can do the job?

What I have tried:

there is a way to save the html of browser in a file and then read that by java, but it really is not the best solution.