How Do CD Keys Work?

What is a CD key?

A CD key (also called a product key, game key, or serial key) is a code tied to one license of a game. Originally these codes were printed on the box or a card inside it, next to the physical CD — hence the name. Today most keys are sold and delivered digitally, but they still work the same way: the code unlocks a copy of the game on a specific platform.

How activation works

After buying a key, you redeem ("activate") it on the platform it was issued for:

• Steam— open the Steam client, go to Games → Activate a Product on Steam, and enter the code.
• Epic Games Store— use the "Redeem Code" option from your account menu.
• GOG, Origin/EA App, Ubisoft Connect, Battle.net— each has its own "redeem code" screen in the client, usually under your account or library settings.
• Xbox / PlayStation— codes are redeemed from the console's own store using "Redeem Code" or "Use a Code".

Once redeemed, the game is permanently tied to your account on that platform — the key itself is single-use.

What to check before buying

• Region lock— some keys only activate in specific countries. Store listings usually say "EU", "US", "Global", etc. Looti shows this on the offer when it's known.
• Platform— make sure the key is for the platform you actually want (Steam vs. Epic vs. GOG are not interchangeable).
• Seller reputation— buy from established resellers with buyer protection, not unverified individual sellers.