
watchOS 26 includes a feature that lets you know if you're using an Apple Watch charger that is not optimized for the fastest charging speeds.

According to a new Apple support document, if your Apple Watch detects a charging experience that could be improved, a Slow Charger message will be displayed in the Battery section of the Settings app. Instances of slow charging are shown in orange, while fast charging speeds are displayed in green.
Apple says that the Slow Charger warning simply means that you could get faster charging speeds with a higher-wattage charger, and it does not mean there is something wrong with a slower charger.
Apple recommends a USB-C Power Delivery charger and the USB-C Apple Watch Magnetic Charging Cable that came with the watch for the fastest charging.
Article Link: Apple Watch Gets Slow Charger Warnings in watchOS 26