1.) Go to your Steam profile page. 2.) Right click your avatar picture and select the "Copy Page URL" option on the drop menu. 3.) Go to https://steamid.io/ and right click to paste the above URL in the proper input box. Steam ID = [STEAM_0:0:00000000] Steam ID3 = [U:0:00000000] Steam ID64 =  = the numbers to steam profile web url. Example : steamcommunity.com/profiles/00000000000000000/ Looking for another players Steam ID. If your playing a Source Engine game, like Counter-Strike or Left 4 Dead 2, then open the Developers Console and type status then click submit and it will show their steam ID if they are still in game, then you can just take a screenshot of the Console. If the player leaves you can open your Steam Client Window, and hover the mouse over Your Steam Name at the top that comes after the Store, Library, and Community tabs, then select the FRIENDS option from the drop menu and click on the Recently Played With tab to find them and do steps 1 - 3 but with their Steam Account & Avatar.