For chess players seeking to improve their game, nothing is more helpful than the study of problems. Chessproblems strives to be the best chess problem and puzzle site on the internet. Users interactively solve and explore all varieties of problems through an interactive applet. Comments can be left on individual problems -- a process that leads towards a high level of quality over time. Any user can contribute new chess problems through an interactive editing system (more info). The interactive problems support multiple solution paths, refutations, comments, and real-time refutation generation on some mating problems.

How To Use Chessproblems

The first step is to find a good problem to tackle. Problems are rated from 500 to 3000, with 500 being the easiest rating. On the front page you'll find a list of the most recent problems. This can be an easy place to start, or by going to the problems page you can search with more precision. Once you click on a problem, you should see a big chess board come up. (If you don't see this, you probably have a problem with your browser's Java plugin -- see the Requirements section below.)

Now that you see a chess problem, how do you solve it? The first thing to notice is that there are two types of problems: "Mate in X moves" and "find the best move." In the mating problems, you'll see a big box up to the left of the board that says "Mate In" and then has a number next to it. In these problems, you must mate your opponent in this many moves (note: this only counts your moves, not your opponent's. "Mate in 3" means you get to move three times, and your opponent moves twice.) In the best move problems, you must analyze the board and look for the best goal yourself. Sometimes there may be text accompanying a problem giving you additional instruction, like "find a draw." Note that just because a problem doesn't intruct you to mate in a certain number of moves doesn't mean that you can't checkmate your opponent.

Next, figure out whose move it is. To the left of the chess board is a box with "To Move" written inside, and a pawn next to it. Whatever color this pawn is, it's that team's move. When you think you know the solution, click on the piece you want to move. You can either click and drag the piece to its destination, or click once on the start and again on the end square. As you move your mouse over possible destinations, you'll see a green highlight for legal moves and a red highlight for illegal ones.

After you move, one of several things may happen. If you have solved the problem, you will see the chess lady say "Solved." If you're not yet at the end of the problem, the computer will typically respond -- and you won't yet know whether you're on the right track or doomed to failure. Sometimes, however, you may have done something the problem's creator didn't expect, and you'll see "Off Path." This counts as a failure. Except in "Mate In X" problems, problems typically only account for the most probable moves. Anything that deviates from this is considered wrong. If you disagree with an unprogrammed move being wrong, and think you've found an alternative correct solution, please leave a comment.

Viewing the Solution

Sometimes a problem is too hard, and you want to give up and see the answer. Or perhaps you solved the problem, but wish to experiment with alternate paths. There are two ways to view the solution: "Animate Solution" and "Navigate Solution." (You can find these options under the popup problem mode menu that by default says "Play.") "Animate" will move the pieces for you from beginning to end. If there are multiple solutions, it will only show one. "Navigate" lets you explore the whole tree. When you choose this option, two things will happen. First, the board will show arrows for piece movement. Green lines indicate a correct path, red ones a failure, and gray a path that was something you tried that wasn't originally on the move tree. The other feature of the "Navigate" mode is a view of the full move tree. This you will see to the right of the chessboard. The colors here symbolize the same things as the colored arrows on the board. Your current location is highlighted with a yellow circle. A move that gave check shows a red star, and a checkmate a purple star. In this mode, you can move around by dragging the pieces on the board as normal, by clicking on places in the tree, or by using the arrow keys.


To unlock the full benefits of the site, free registration is required. When logged in, problem attempts get remembered, so when you view a problem you can see how many times you've tried it before, and how many of those attempts were successful. This information also lets you search for problems that you've not tried yet, or not solved. By logging in, you can also leave comments on problems. A forum also exists for general discussion of the site.


Chessproblems requires Java 1.4 embedded in the web browser of choice (why?). If not already installed, this can be downloaded for free at Sun's Java page. The applet has been tested on Firefox, Internet Explorer, and Safari.

Problem Ratings

Problems are rated from between 500 and 3000, with 3000 being the hardest possible problem. This rating system is not based on any subjective judgement, but rather as a function of the solve ratio to date. In other words, how well people do on a problem determines its rating. Thus, a problem's rating changes over time. The exact function will probably change over time as we get more data. The intention is to roughly correlate a problem's rating with the standard chess rating systems, such as FIDE. If a problem is rated 1500, a player of 1500 strength should be able to solve it about half the time within a couple minutes.


Three piece sets are currently available. "Minimal" shows your basic black and white shapes. "Classic" is the same set with a little shading. "Earth" is a beautiful, slightly impressionistic set. A popup menu in the problem applet lets you choose between the sets. (The chosen set should stay between problems, but may need to be reset between visits. This will eventually be stored in the database.)

By checking the Sound box, you will hear some contextual sound effects while solving problems.


Chessproblems is based on goproblems.com, a site designed for studying the game of go. For Chessproblems, the core code has been significantly rewritten and upgraded. In July 2005 the site first opened as a semi-private beta.