How do you know when caffeine is actually out of your system?

Hi everyone! I’m curious if anyone here has tried reducing or completely quitting caffeine. What worked best for you — stopping all at once or gradually drinking less?I feel like one of the hardest parts is knowing how much caffeine you’re actually consuming and how long it stays in your system.If you’re also trying to cut back, there’s a caffeine tracker that lets you log your drinks, see your estimated caffeine level throughout the day, and gradually reduce your intake:https://play.google.com/store/apps/details?id=com.cleveroad.caffeine_tracker&hl=enHas anyone tried tracking caffeine while cutting back? Did it actually make the process easier? ☕