You Can Now Completely Remove Games From Steam
Last year, Steam finally allowed you to hide games in its Steam library to reduce clutter. Now you can finally completely uninstall the games you don’t like.
Deleting the game is a little confusing, but now it is quite possible. Simply go to the Steam Support screen (Help> Steam Support), select the game you don’t want, then select I want to permanently remove this game from my account. This should make it a little easier to clean up trash that you never plan to play again. However, keep in mind that when you uninstall a game, it disappears forever and you will no longer be able to download it or play it.
Steam now allows you to permanently delete games from your account | Neogaf via PC Gamer