I've just been playing for fun online a little bit, and was wondering how hard the computer I've been playing against is. NOTE: This was made for a javascript competition, and doesn't include castling or en passant capture.


  • It's probably quite bad. I won the two games I just played against it, and I'm not that good. But, no castling or en passant means that it's not really playing chess, so it's not like I can give you an approximate elo to compare with other chess players or engines--it's simply not the same game as normal chess. Mar 29, 2014 at 4:13

3 Answers 3


As a programmer, trying to write a chess engine by Javascript which runs on client's browser is very interesting. It has only 1018 bytes!

The engine doesn't obey the rules thoroughly (however we can ignore at this time). On the other hand it plays immediately and doesn't consume time to find better moves. It just trying to avoid obvious and basic blunders and probably it can find mating moves.

I suspect it uses any popular approach such as min-max search trees to evaluate moves. It's a very simple program and most of newbies can defeat it easily.

So, if you're not a programmer and following for a chess engine, don't count it as a real chess program.


It does have the capability to spot basic mating threats as far as I saw. No opening theory book is supported, thus its opening play is terrible. It has a bad evaluation function, as it was not able to spot simple threats and does not recognize what is weak or strong move. Defending capabilities are low. I won fast so I can not comment on its endgame or attacking skill. In short, it plays as someone who just learned the game rules ( except en passant and castling, of course ).

Hopefully this helps.

Best regards.


I didn't play a full game with it (mainly because of having to scroll to see the full board), but I'm not so impressed. Also, there is a bug in it which prevents long castle.

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