If you are using the non-Steam "Legacy" version of the game (often found on old physical DVDs or the Euro Truck Simulator 2 website ), you may already have a key stored on your system.
While many websites claim to offer free product keys for version 1.40.4.8, these lists (often found on sites like Scribd) are usually already used or fraudulent. To safely obtain a key, you should use official or reputable sources: Source Type of Key Account-Bound Euro Truck Simulator 2 1.40.4.8 Product Key
The product key is required to the full version of the game. Without a valid key, you are limited to the demo version, which severely restricts play time and features. If you are using the non-Steam "Legacy" version
Version 1.40 was a milestone update for developer SCS Software. It focused primarily on a New Visual Lighting System Without a valid key, you are limited to