Two APIs, One Tool
This tool exposes two completely different vibration APIs in one UI. The phone tab uses navigator.vibrate(pattern), which drives the single linear or rotary-mass vibration motor inside a phone using a sequence of on/off durations in milliseconds. The gamepad tab uses the Gamepad API's vibrationActuator.playEffect('dual-rumble', {...}), which drives the two independent motors inside an Xbox-style or PlayStation-style controller. There is no overlap between the two — a desktop with a connected gamepad will report "Vibration API not supported" for the phone tab but happily rumble the controller, and a phone with no controller connected will do the opposite.
Vibration API (Phone Haptics)
navigator.vibrate() takes either a single number (milliseconds to vibrate) or an array alternating vibrate/pause durations. It is supported on Android in Chrome, Firefox, and Samsung Internet, but not on iOS Safari — Apple has never shipped it, citing privacy (the vibration motor can be used as a fingerprinting vector). On Android, patterns with alternating durations under ~40 ms tend to blur into a single buzz because the motor spin-up time exceeds the pause. For crisp multi-pulse patterns, keep vibrate and pause durations above 50 ms each.
Gamepad Dual-Rumble Explained
Xbox and PlayStation controllers have two internal rumble motors with different weights on the shaft. The "strong" motor uses a large eccentric weight and produces low-frequency bass-style rumble — you feel it in your palms. The "weak" motor uses a smaller weight and produces high-frequency buzz — you feel it in your fingertips. Games blend the two for cinematic effects: explosions weight heavily toward the strong motor, shotgun reloads toward the weak. This tool lets you test each one independently so you can isolate a failed motor — a common fault in older Xbox controllers where one of the two solder joints cracks.
Why Some Controllers Show No Rumble Support
Chrome and Firefox expose vibrationActuator only on controllers that support the "dual-rumble" effect over their specific HID protocol. Wired Xbox controllers and official DualShock 4/5 controllers usually work out of the box over USB. Bluetooth can be more fragile — some BT stacks drop the rumble descriptor, in which case the browser reports hapticActuators (the older API) but not vibrationActuator (the newer one). Cheap third-party controllers often report the buttons and axes correctly but have no rumble hardware at all, even if the marketing text claims otherwise.
