Your steamid is a unique number that belongs to your steam (valve games) account. It’s how you’re banned, and it’s how admin plugins know you have admin access. It comes in the form of STEAM_X:X:XXXXXX where Xs are digits.
To find your steamid in any valve game:
- Join a game online (it must be an internet game, not a ‘new game’ game)
- Open the console by presing the ~ key (next to 1). You may need to enable this in Source games by going to Options -> Keyboard -> Advanced -> Enable developer console
- Type: status
- Press enter
- Search for your name, and copy the entire steamid (STEAM_X:X:XXXXXX – including the STEAM part) into the admin application or ban appeal
If the game has a statistics page (hlstats, psychostats, etc) you can also find your steamid there.