As others have pointed out already, it is impossible to sell the games you bought on Steam. You don't buy keys there, you just get games that are instantly activated on your account. The latter you might try to resell, but it's a) not OK according to EULAs, b) highly impractical, as you would have to create a separate account for each of your games.

Now, reselling games was possible via Steam Gifts, but Steam's policy on these was changed about two years ago. Gifts no longer go to your inventories, instead they are immediately sent to the recipient. If they don't accept it, you just get a refund. And as far as cross-country gifting is concerned, if there is a serious price disparity between regions, this option is simply unavailable.

This does not apply to pre-change gifts, so if you have anything left, you can still do Steam trades. If you'd like to swap your stuff for extra moolah, you can put them up on sale on gaming marketplaces, such as G2A. There are millions of customers there, so I'm pretty sure you'll sell leftover copies in no time.

In most cases you can not. If you mean buy a game, play it, and then sell or trade it then no. If you purchase or obtain a game as a gift item however then you may trade or (somehow) sell it.

You cannot sell your games from your library, because digital distribution is actually more like a "renting for life", as a result, a game added to your library is activated for your account and its owner cannot be changed.

Edit: The condition described in below paragraph is no longer valid as Steam have changed their policy for purchasing gift games.

%3E However, you can store games in your inventory instead of library. The games kept in inventory are not activated. As a result, the owner of the game can change if you give it to someone else. To buy a game as an inventory item, you must choose "purchase as gift" and then "keep the gift in my inventory to send later" during the purchase. The games in your inventory are available for trade after some period of time of purchasing, and they are available for gifting right after you buy them. People can trade the gifts, this can be both in-game items and games themselves. However, you cannot sell these games on community market.

There are some people selling their games for real money / over Paypal and such but this is based on personal trust and can be risky depending on the peer you're trading with.

Adding on to these othe lr answers: If you want to let your games be playable on another account, there is Steam Family Sharing. Just authorize it on you or your pals computer under the settings menu, and then have them do the same thing. Ta-da! Now they can play your games!

at this moment it's not possible to sell games you have installed into your library, you can sell of things from your inventory though, since those can be send to other users...

but, i've heard rumours that selling stuff from your library could become possible in the future, especially if you're in europe since we have different laws than in the states and if we buy something law says we should be able to sell it again if we want to. (that's why it's legal in europe to sell your software licenses if you don't use them anymore; while in the USA you're bound to the EULA where those rights are withdrawn from you; in Europe the rules in EULA's only apply if they do not break any rights you have by your country's law or European law (which goes above local law).

therefore; if a eula says you don't own what you buy, it's not valid anymore; you payed for it so you own it, it's not a hired license or something, becaues you only payed once and it's not a subscription, also there is no end date mentioned on those licenses or when you bought them there was no timeframe given for its validity. In the USA this protection by law doesn't exist; if you sign something that says you don't have any rights anymore, then you lose your right... (in the us you often sign on your employment-contract that you cannot sue your employer; if in EU this is on the contract it doesn't matter; you can sue him anyway and such a note on the contract would already be used to show the employer is choking it's employers)

It is against agreement you have to sign when creating account on steam. You can only sell games from your inventory but those in your library you can’t.

At least officially. I’ve seen Steam accounts on online auctions but i’m not sure if you can trust that what you pay is what you get. Sellers account info has to stay private for public else he risks getting banned because of doing something against the Steam agreement. This puts buyer on risk, since account information he gets emailed on priv etc., might be fake or even worse, stolen.

No you cannot do this because when you buy a game on Steam you are purchasing rights to play the game on Steam, not own it. If you want to sell/trade the games( maybe sometime in the future) you should get physical discs.

Cheers!

The other answers are pretty comprehensive, however, Steam is currently working on a reselling system, whereby another player can buy a used game from you as a purchase, and a percentage of the payment goes to Steam and some to the developer.

EDIT: Based on a few comments from people asking where my sources were, I looked through some of Extra Credit’s videos on their YouTube channel and found the following 2 videos which relate to the issue at hand. The direct reference stating that the feature is in development I have not been able to find.

https://youtu.be/aKSFPRaJpzA https://youtu.be/xnGsbJaM7GU

If they are in your library no.

In order to sell or trade games you would need to buy them as gifts. You then have them as an item in your inventory along with your trading cards and other steam objects.

Once you have activated something and placed it into the library it is yours forever (unless you refund it).

You can hide or remove things from the library, but you can not trade them away.

No, you can’t. You have to sell your actual account to somebody (which isn’t really allowed but, don’t let steam know and you’ll be fine) They have a 2 week return policy if you have less than 2 hours in a game so, keep that in mind.