Chess zone of control (ZOC) / territory


I made a web app a few months ago to help me visualize the zone of control (ZOC) / territory / controlled squares of various lines and positions.  I originally made it just for my own use but I found it so helpful I thought I’d share it with everyone.


I keep it open on the side and it really helps me deciding where to move my pieces and avoiding blunders.  My positional play has improved dramatically and as a relative beginner it also helps me see the pros and cons of different openings.


For example, here is e4 (wider coverage) VS d4.

Or Ruy Lopez (strong development for white).

Or any position and other variations like Chess960 (has basic FEN support).


I was looking for this tool before and I hope someone else may find it as useful as I do.  Feedback/suggestions welcome.


Wow. Fantastic. Thanks for sharing the app. You're a great guy. Do you envision to share the code (maybe so we can alter the color coding)?

SC2Chess wrote:

Wow. Fantastic. Thanks for sharing the app. You're a great guy. Do you envision to share the code (maybe so we can alter the color coding)?

Hey thanks for the kind words.  I'd love to collaborate and keep improving this tool since I still use it quite often.  Just curious, what ideas for color coding did you have in mind?  It could be a very simple change.


I was just thinking that with all the colors superimposed, it becomes too dark, and the contrast is lost. It might be better with a lighter background. Great work nonetheless.


I have a metric for determining relative positional strength I call the Space Control Index.  Draw a line horizontally across the center of the board - the 50 yard line.  You get a point for every one of your opponent's 32 squares that one of your pieces is covering, and vice versa.  If you have, say, two rooks doubled on an open file, or a queen backing a bishop on a diagonal, both pieces can rack up points; their force field extends to the square that an opposing piece is on, but no further than that. 


Thanks for all the feedback so far! I wanted to let you all know I've released a new version of the tool with:

  • ability to turn off the board shading
  • undo/redo buttons
  • display for each side's # of controlling squares.

I hope some of you find the new features as useful as I do.  As always, any feedback is appreciated!


I just wanted to program that!


This is great! Thanks for making it! I envisioned something like this, but can't code well enough to make it. Definitely a nice learning tool!


Ten years ago a man I played at the Austin City Championship explained this to me.  He added up all the squares in the opponents half of the board that his pieces attacked ( including squares occupied by the opponents pieces ). He called this his Attack Score.  

I used this for several years. Abandoned it after studying a game Anand Caruana , St Louis. Believe the date was Aug 06, 2011.  Calculated after every even move 10, 12, 14, 16, 18, 20, 22, 24,  & 26 Black's Attack Score was greater than White's , usually substantially greater. Yet the game ended at move 29 with a White ( Anand ) victory.

Searching my old records may find the name of the gentlemen who used this.

I've read that alphazero highly values piece mobility. I'm trying to develop a metric that simply totals all the spaces to which each piece ( not pawn ) can move. This might be a measurement of development.  Unfortunately my programming skills are rusty and I've never done chess in Python.


Looks like a great app. I'm a dinosaur and do not have a cell phone, so don't use apps. (Well, even when I did own a cell phone, I didn't use apps either). I lean more towards the "line" method mentioned in post #5.

Here's a video from GM Yasser Seirawan. It may be similar to what is mentioned in post #9 above. It explains controlling squares on the enemy's side of the board, how pieces get their relative values, and the best opposing squares for each piece to occupy. It is a bit long, close to an hour; but well worth reviewing if you are a beginner. I think even intermediate players would gain by this refresher.


It's so sad that your site is down, it helps me learn chess a lot.