Not that I know of. Only way is to actually enter the key into steam.
How the hell did you get so many keys anyways :o

give them all to me, i'll tell you..

just post it on pastebin and give us a link :D

Ninjas ftw

If they are from bundles, you can't create a giveaway for em, unless the entire bundle is unused. Just the rules.

You can however post them here on the forum.

If they are from a site like amazon, then you can give them out. those are fine.

Only way is to write to Steam Support, they can tell you but not sure if they will be happy to do so many ;)

Also read what Gramis commented here.

Well, there's no harm giving me one, for testing purposes only of course.

ninjas suckz
at least make puzzle or somethin' with pastebin link or what

Also if you write to Steam Support, be sure to ask them if it's possible before you send them any keys.

Do you know which games they are? No matter if they're used or not...

Give me a game and i say to you yes or not duplicated.

no

I would love way to check it on steam.

If there's anything from Oddworld pack, you may pass it to me to check :)

I could participate in the testing :D

GO Ninjas!

6LD8J-T8I9B-85VBL

DDAN0-FZIN8-A0ZVF

QFAJL-J28FG-6G8LH

MF2FX-6WRXI-DNBJ4

GQWID-FZHG2-P95G9

So from the comments I understand that I have no possibility beside contacting steam for it?

Tonight I love humping dead threads.

You can tell if a key has been used by just USING IT. But if you don't want it you can cancel the download and it'll count as unused.

You can do a forum giveaway, the most fast bastard you have it and with luck the key will work... :D

add me on steam and ill tell you what keys are used and what arent :D

u can enter code and if you have thatgame and its valid it would say that game is allready in your inventory so you will know its valid :)

Send me and check valid XDXD

I suppose not, but you probably should close this thread, since it's already 5 months old and nobody has an idea how to know if it's used.