MIDI Tester

What your controller is actually sending

When a MIDI device does not work, the useful question is where the signal stops. This shows every message arriving at the browser, so you can tell a silent controller from a working one that your software is ignoring.

What you will see

• Note on and note off, with the note name, velocity and channel. Velocity is how hard the key was struck, 1 to 127.
• Control change for knobs, faders and pedals, with the CC number and value. The sustain pedal is CC 64.
• Pitch bend, centred on zero and running roughly −8192 to +8191.
• Aftertouch and program change, if your device sends them.

The two-octave keyboard lights up for notes in its range. Notes outside it still appear in the log.

Browser support is limited

The Web MIDI API works in Chrome, Edge and Opera. Safari and Firefox do not support it — there is nothing to configure, it simply is not implemented. If the page says the API is unavailable, switching browser is the fix.

How to use it

1. Connect your device first, then load this page.
2. Press connect and allow MIDI access when asked.
3. Play something. Notes light the keyboard and every message appears in the log.
4. Move every control — knobs, faders, wheels, pedals — to confirm each sends what you expect.

Devices connected while the page is open are picked up automatically; there is no need to reload.

Common uses and tips

If nothing appears

• Close your DAW first. On Windows especially, MIDI devices are often claimed exclusively by one application.
• Check the browser. Safari and Firefox have no Web MIDI support at all.
• Check the cable. Many USB cables sold with instruments carry power only and no data.
• Check the device's own channel setting. A controller set to a channel your software is not listening on looks broken and is not — the log here shows every channel.

Diagnosing common faults

• Stuck notes — a note on with no matching note off. Visible immediately in the log.
• A dead key — no message at all when pressed, which separates a hardware fault from a mapping problem.
• Uneven velocity — play each key at the same strength and compare the numbers. Large differences mean the sensors need calibrating.
• A jumpy knob — values that jump around when you are not touching it usually mean a dirty potentiometer.
• A reversed pedal — CC 64 sending 127 when released rather than pressed. Most keyboards have a polarity setting for this.

Questions people ask

My MIDI device does not appear.

Close any DAW first — MIDI devices are often claimed exclusively by one application. Then check you are in Chrome, Edge or Opera, and that the USB cable carries data rather than power only.

Does this work in Safari or Firefox?

No. Neither supports the Web MIDI API. Chrome, Edge and Opera do.

What is velocity?

How hard a key was struck, from 1 to 127. Playing each key at the same strength and comparing the numbers will show whether the sensors are even.

What is CC 64?

The sustain pedal. If it sends 127 when released rather than pressed, the polarity is reversed — most keyboards have a setting for it.

Do I need to reload when I plug something in?

No. Devices connected while the page is open are detected automatically.