How does LiChess know that a "Player has left the game?"

Sometimes they re-join. What's going on?

yeah... it's embarassing when lichess says the guy has left the game... and i start saying smack in chat, and then they rejoin....

oops. but often they've left cause they're merely humiliated, idiotic, moronic and other onics.

Do you guys claim a win or draw when this happens? I claimed a win the other day and felt bad about it. But wonder why they left and wonder if they didn’t leave to go plug the position into stockfish or something

I claim a win when I'm obviously winning, if not I claim a draw

Many of us have bad or unreliable connections. When I get that message I assume the opponent will be back soon, and often they are. I have gotten disconnected myself a few times, gone through the irritating routine to get reconnected, which for me means shutting down the browser and re-booting, and once or twice for rapid games, I got back in time to continue. So I don't always figure it's one of the onics -- though sometimes it is, like when they blundered a piece. I always claim the win. What the heck? I've lost enough games getting disconnected by no fault of my own.

There was this time it said they were disconnected and then they played while disconnected- it was weird.