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PING

There is a console box on the Play page. Type /ping there.
/ My ping was 30 milliseconds the first time I tried it. I tried it again later and it had dropped to 20 ms.

If you want to know your own ping just open command prompt and type
ping chess.com
Chesscom used to allow you to check other players' pings but they inexplicably removed the feature.

If you want to know how good your connection is for play, Windows Command Prompt won't tell you. It will ping a general Chess.com web server, not the server used for your game.
If the ping command isn't working in Game Chat, go to Play and open the console (the keyboard icon) to the lower right of the board), then type /ping.
How do I check the ping on chess.com? typing “/ping” in the live chess chat box is not working.