The exact menu phrasing depends on which version of Factory Idle you are playing (Kongregate, Armor Games, or the downloadable standalone). Follow this generic flow:
The User Key is a unique, personal identifier tied to your specific game account and progress. Think of it as your digital fingerprint for the game. Because Factory Idle is often played in browsers (like on the official site or Kongregate), local cache clearing can sometimes wipe your progress. The User Key acts as a bridge, allowing you to: factory idle user key
Factory Idle has been around for many years. Over time, the game has changed hosts, switched from Flash to other technologies, and updated servers. Players who took a break from the game often return to find that their old "auto-save" is gone because The exact menu phrasing depends on which version
If you find yourself on a fresh screen, look for a "Restore Game" or "Input Key" field. Entering your saved User Key will pull your existing factory data from the server. Why the User Key Matters for Strategy Because Factory Idle is often played in browsers