City Car Driving originally used a manual serial number and activation key system. Unlike modern games that link to an account automatically, the older versions required a multi-step handshake between the software and the developer's servers.
Upon startup, the game should prompt you with an "Activation" or "Registration" screen.
Once the website generates your long-form activation key, copy and paste it into the "Activation Key" field in the game menu. Troubleshooting Common Activation Issues
If you are looking to get behind the wheel of one of the most realistic driving simulators ever made, you likely need a valid activation key to unlock the full experience. City Car Driving is renowned for its punishingly realistic physics and its focus on teaching real-world traffic rules.
The activation key is tied to your motherboard and CPU. If you upgraded your PC, the old key will no longer work. You may need to request a "deactivation" or a new key from support.
Be extremely cautious of "key generators" or "activation links" found on third-party forums. City Car Driving uses a specific hardware-ID check. Most "free" 121 activation keys found online are either outdated or bundled with malware. The safest way to play is through the official Steam version, which bypasses the manual key entry system entirely.
The developers have largely moved away from the old manual key system. If you have an old serial number, you can often "recover" it or request a Steam key from the official developers to avoid manual activation entirely. ⚠️ A Note on Security