WHAT IS THIS KEY FOR!!!!!!!!!!!!!

not that i know of

--------------------- deleted comment for my own sake.

if u try them and its say u already have the game, then it still works. at least that happend when i tried a few with a friend

there's no way to tell what the key is for or if it has already been used, until you try to activate the key.

example: you've got a key for The Ship

(a) you try to activate it on an account that already owns The Ship -> it will tell you that the account already owns the game (but not if the key is used / unused)
(b) you try to activate the key on an account that does not own the game
(b) (1) -> the key is now either bound to the accound (if unused)
(b) (2) -> you get the message that the key is alreday used (if used)

Well, your best bet would be to find a trusted friend who has a ton of games activated and have them check to see if it registers- that way the odds of them activating are pretty low. Otherwise, if you know where they're from, you could try asking the support for the place you got them, but that's no guarantee. I know Humble Bundle is helpful, not sure about others.

yeah would be hard to know what key that is... usually, i just drop those kinda key in my chatroom ... it's for giveaway anyway

You need to ask a friend who has zillions of game in their lib to try activating it for you. Best chance of finding out.

I think a few things are being confused here.
There's two different things you might want to determine about a key.

1) Whether it's used.
2) What game it's for.

(2) you can figure out probably fairly reliably from the method SquireZed mentions. It won't tell you if the key is used or not. (1) you can't find out, you need to keep track of that yourself.

There's nothing much you can do other than contact support. I suggest you do that. :)

Try and activate the keys yourself, if you don't have the game yet, one more for the backlog, if you have it, you will know what game it is, i'd just drop the key in a chat or have a friend that doesnt have it try and activate, like you said, rather that then get a bad rep ;)

If you're sure they're unused but not sure what game they're for, as pointed above, find someone with massive amount of games to try them out, as it's likely that he'll already own the game and not activate it. There's no way to check if key is used or not without activating it though.

If you have no such friend, you can always add me, I'm glad to help in such cases.

There is actually a way. Contact somebody who has 4000 or 5000 steam games and ask him to check that key.

He must have that game at 99'9%, so he will get a message that he already owns "XXXXX" game.

My heart <3 (?

Just trade all the keys. For like one key. Here I have 7 keys I don't know if they work or not. Or what they go to. But hey if you want to give it a shot.

Like others said, Steam Support (but they might not answer at all).

If you can live without CV, you can always try here. Or just spam some friend with "got keys, but might be used".

I just got a reply from Steam Support, with a similar question. Have a pile of leftover bundle keys, I know what games they are, but not sure they are all unused. :)

We apologize for the delay.

Unfortunately, we are unable to verify for you which keys have been used.

:(

If you only want to know what the games are, like everyone suggested you'll need to ask someone you trust, who owns all the bundle games... :) Good luck... :)