Fitbit Flex features five LED indicator lights. The lights behave differently depending on what the tracker is doing.
The indicator lights illuminate as you hit 20% increments towards your goal. Tap your Flex to see your progress. When you reach your goal, Flex will celebrate by buzzing and flashing its lights.
For more information, see Setting goals with Fitbit Flex.
Sleep ModeWhen you tap your Flex rapidly for one or two seconds to enter sleep mode, it will vibrate and display two slowly dimming lights. During sleep mode, two blinking lights alternate. After you tap your Flex rapidly to exit sleep mode, it will vibrate and flash all five lights three times and then display a spinning light pattern. For more information, see How do I track my sleep?
ChargingWhile your Flex is charging, an indicator light will pulse to show the battery level every few seconds.
Each indicator light represents progress towards the total charge. When the Flex has charged completely, all 5 indicator lights will blink. For more information, see How do I charge my Flex?