USB multimeters (power meters) are dongles placed in-line between the charger and the device. They feature LED/LCD screens displaying Voltage ($V$), Current ($A$), and often calculated Wattage ($W$).
Advanced testers (such as the FNIRSI FNB48 or Avometer models) can record voltage and current curves over time and even detect the specific protocol handshake (e.g., identifying if a PD 3.0 handshake occurred). how to check charger wattage
Older or simpler chargers display a single value. USB multimeters (power meters) are dongles placed in-line
The label contains several lines of text. The user must locate the line beginning with or an arrow symbol ($\rightarrow$). how to check charger wattage
