About this tool
Gamepad Tester reads controllers through the browser's Gamepad API, which only shows values after the operating system has applied its dead zones and scaling. This page talks to the controller directly over WebHID. That exposes the raw stick numbers before any processing, the battery level, the firmware version numbers, gyroscope and accelerometer readings, the touchpad on a DualSense, and the calibration data stored in a Switch Pro controller.
This version supports two controllers: the DualSense (PS5) over USB and Bluetooth, and the Nintendo Switch Pro Controller over USB. For the Switch Pro, the page sends a few setup commands so the controller starts sending full reports, then reads its factory and user calibration from SPI flash without writing anything. The output tests send rumble, light bar, player LED and mic LED commands, but only when you press their buttons. None of them has been run on real hardware yet, and the Bluetooth output checksum is unverified.
The report layouts come from community reverse-engineering and the Linux kernel drivers, not from an official specification, so a firmware update can change them. Everything runs in your browser, and the page never writes calibration to the controller.