The best way to report someone is via the (!) icon as described below.
You can also go to Chess.com and click the "Help" link at the bottom left. On mobile browsers, first open the navigation via the menu button on the top left.
How to Report
Hover over their username and click on the (!) icon
This will open a new window where you can select the reason for your report
Select the option that best describes the reason you are reporting the person, and write a brief description of what happened in the text box.
When you have made a selection, the report button will light up.
Click the report button, and the report will be sent to the Chess.com Abuse and Fair Play teams. When the user gets enough reports of this kind, their account will be flagged for review, and may be closed or suspended.
If the person is bothering you personally, be sure to check the ‘block’ box so that they will no longer be able to chat to you or challenge you to games.
If you would like to block someone without reporting them, you can select the block icon from their profile instead:
To see these steps for Android, click here. For iOS click here.
If you encounter anyone doing any of the following:
Anything lewd, sexually inappropriate, or pornographic - this includes text, images, links, etc
Anything offensive, threatening, or intentionally discriminatory to any race, gender, sexual orientation, etc
Anything slanderous, threatening, or malicious toward any user
Anything "spam" (links to commercial websites where not approved, etc)
Cheating, stalling in games, quitting games, or sandbagging.
Please report the individual!
Here's a video on how to report or block another member:
Mobile
Tap on the member's avatar in the game to show the list of options:
Tap 'report' then select from the dropdown in the next menu the option that best describes the reason you are reporting the person:
Be sure to write a brief description of what happened in the text box.
When you are ready, tap the report button, and the report will be sent to the Chess.com support team.