how do I tell if a person is cheating or not?

They're either trolling (like whoever decided to make the account @stockfis ) or they're just wimps who can't play with their own brains.
You can't tell, not for sure. The vast majority of players don't cheat, so you don't need to worry so much. And every time someone makes a good move against you, that doesn't mean they're cheating. If you have a game that makes you very suspicious, there is a process for reporting a suspected cheater. Don't make public accusations in the forums

I personaly only one time suspected that my opponent was cheating.
His raiting was much lower than mine.. but he did beat me very fast.. and he did moves at high speed.
Post-game computer analysis showed that he made no one mistakes.. only he was inaccurate a few times.

I personaly only one time suspected that my opponent was cheating.
His raiting was much lower than mine.. but he did beat me very fast.. and he did moves at high speed.
Post-game computer analysis showed that he made no one mistakes.. only he was inaccurate a few times.
IMO, if he played very fast, he's probably not cheating. And at your level of 1500+, I think it's feasible to not make mistakes, so long as the moves are straightforward and not weaving complexity.

boogieman, I just watched your last game: you kept giving away material for free, obviously not checking much on anything, until you gave away a piece and a checkmate at the same time.
So, I would say, if you allow me to advise you, you should forget about cheating issues until you pay attention to what is going on on the board.
Ripley, do you fight cosmic monsters as you before did ? )
I personaly only one time suspected that my opponent was cheating.
His raiting was much lower than mine.. but he did beat me very fast.. and he did moves at high speed.
Post-game computer analysis showed that he made no one mistakes.. only he was inaccurate a few times.
How many moves? Do you have the games? Might have been a trap

I personaly only one time suspected that my opponent was cheating.
His raiting was much lower than mine.. but he did beat me very fast.. and he did moves at high speed.
Post-game computer analysis showed that he made no one mistakes.. only he was inaccurate a few times.
he could have been extremely underrated.

Because in the future I would like to know well how I could see a cheater or not?
The guy on your picture take steroid! did you know that?

Well I ahvent suspected anyone of cheating seriously but a load of members have been caught cheating.
Once i got 20 rating points by compensation for unfair losses together. I think i hav earned atleast 200 rating points by compensation for unfair losses.
Because in the future I would like to know well how I could see a cheater or not?