To determine if the «Strapless Strap-On» vibrator by Happy Rabbit is charging, you can follow these general steps, as specific instructions might not be available without the product manual:

1. Check the Charging Port: Ensure the charging cable is properly connected to both the device and the power source.

2. Indicator Lights: Many vibrators have indicator lights that change color or blink when charging. Check if your device has such lights and observe their behavior.

3. Manual Instructions: Refer to the product manual for specific charging indicators, as different models may have unique ways to signal charging status.

4. Weight and Feel: Sometimes, a device might feel slightly warmer or heavier when charging due to the battery activity.

If you don't have the manual, contacting Happy Rabbit's customer support or checking their official website for product details might provide more specific guidance.