If you still have the original disc and jewel case, your product key is printed on the manual or the back of the case. However, be aware:

(Five groups of five characters). These are used for older non-Steam versions, such as 1.15.1. Steam Format: XXXXX-XXXXX-XXXXX

If you bought the game online, the product key is sent immediately to the email address used during the purchase. If you cannot find it: Euro Truck Simulator 2 Check your spam or junk folders.

: For older versions like 1.15.1 downloaded outside of Steam, enter the key directly within the game's startup menu. If you are offline, you may need to use the Offline Activation Tool to generate a checksum file.

The most reliable way to access older versions like 1.15.1 today is through Steam, as it manages licenses automatically without requiring manual key entry every time. Redeem on Steam: Open the Steam client, go to Activate a Product on Steam , and enter your legacy key. Downgrade to 1.15.1: Right-click "Euro Truck Simulator 2" in your Properties temporary_1_15 - 1.15.1 incompatible mods from the dropdown list.