MIDI Tester
Plug in a MIDI keyboard or controller, press Connect and allow access: played keys light the virtual keyboard while every MIDI message is decoded into the log. Notes that switch on but never off are a classic stuck-note fault.
Connect a MIDI device to begin
Plug in a MIDI keyboard or controller over USB, press the button below and allow access when the browser asks.
| Time | Device | Type | CH | Data | Raw |
|---|---|---|---|---|---|
| Play something — every message lands here. | |||||
How to read it
- Note on with velocity 0 is how most keyboards send note off — the log decodes both as note off.
- Sustain pedal is CC 64, mod wheel CC 1, volume CC 7, pan CC 10, expression CC 11; pitch bend reads −8192 to +8191 centered at 0.
- Missing note-off messages can involve the keyboard, connection, driver or input selection; this alone does not diagnose hardware damage.
- Pick an output under “Send to” and tap the on-screen keys to fire notes at a synth or sound module; “listen only” never sends.
- Use a current Chrome, Edge or Firefox over HTTPS and allow MIDI access. Actual support is detected by this page.
Frequently asked questions
Does it work in Safari or Firefox?
Current Chrome, Edge and Firefox support Web MIDI; Safari generally does not. This page checks the actual API. HTTPS and permission are required. If unsupported, try a browser that provides the API.
My device is plugged in but the list is empty?
Close any DAW holding it first — on Windows a MIDI device is often claimed exclusively by one app. Then check the USB cable actually carries data (many ship power-only), and press Rescan. Still nothing — try another cable/port or check the driver in your OS.
How do I use the log to find a stuck note?
A note on without a matching note off can involve the keyboard, connection, channel selection or driver; it alone does not prove a hardware fault. If both arrive, also check sustain, synth and DAW settings.
What does the velocity number mean?
How hard the key was struck, 1–127: soft and hard presses of the same key should read clearly different values. Always-127 or always-identical readings mean the keybed's sensing is broken or the device is set to fixed velocity.
Is anything I play uploaded?
No. MIDI messages only enter this page's memory for display — no uploads, no accounts, no recording; closing the page releases the device connection.