The proper thing to do is just to win.
Mouse Slip - how to react?
Everybody occasionally does mouse slips. It all averages out, more or less. So NO, don't allow someone to take back a mouse slip, but if it's obvious a mouse slip, I might offer a draw, depending on the board position.
i have had mouse misadventures myself. many many many more times than i care to admit.
i asked for no quarter when this occurs and expect none for i shall likewise show no mercy
I allow takebacks if my opponent said it was a mouseslip, tells me what square they intended to move to, and seems likely to be true(which is 2/3 of the time). Otherwise I just punish their mistake and don't believe a word of their bs. I've never had anyone request a takeback on this website, not sure if it can be done, as i've tried to request after my mouseslips but couldn't figure out how, but it's common on lichess.
If I do a mouse slip, I'll usually resign and just mention in the chat the reason for resigning. If my opponent claims a mouse slip and asks for a draw, I'll always refuse. If they resign immediately, I'll usually give them another game, if they like.
If a make I mouseslip, I just keep playing without mention it, or resign if I fall in an unavoidable checkmate. If my opponent claims a mouseslip, I would concede him a rematch
Mouse Slip - how to react?
Swear a lot, kick the wall.
Ask for draw.
Kick the cat and throw yourself in nearest river.
Another thing you can do is throw the mouse out of the window and smash your pc with a hammer. You'll feel better.
To help prevent your own slips, make sure to click the piece you want to move and then the square where you want to place it. Don't drag pieces to squares. Also, if you're playing longer time periods, consider turning on Confirm Move.
If he/she's a friend and the game is just a friendly game, just let it go. If it's just a normal game however, then I think the principle goes: He/she has tried to gain time by being less than careful and hasty about moving the piece, took a risk and simply failed this time. It's no different than a risky aggressive move that needs to be properly punished if possible. So just go ahead and take advantage of the "blunder."
Couldn't have explained it better myself.
To help prevent your own slips, make sure to click the piece you want to move and then the square where you want to place it. Don't drag pieces to squares. Also, if you're playing longer time periods, consider turning on Confirm Move.
It seems like that is just as bad, sometimes even worse. I've tried that and it's slower. It's easy to click on the wrong square. I agree in slower time controls it would probably work, but so would just dragging the pieces.
When my opponent makes a mistake like that I always try to determine if it was intentional, like a sacrifice. If not I'll usually propose the takeback, not wait for them to ask. If they ask first I'll almost always say yes. No point in winning if it's because of a mouse slip.


I think it sometimes depends, if you have a mate in one and you move your queen but it lands one move short of mate and you lose the piece and the game it is not fair at all, whereas just a minor piece that you accidentally removed or mouse slipped in the opening to a bad square you should just deal with. Whenever you over the board you don't mouse slip, so I guess it is just a downside to online chess.