MIDI Monitor
Watch timestamped, parsed MIDI messages — notes, CC, pitch bend, program change — with filter and local log download.
01How this test works
MIDI tests list your connected instruments and show the messages they send. When you allow access, your browser shares the connected devices, and we start listening for each message as it arrives, with a timestamp.
We turn those messages into musical events — notes played and released with how hard, the sustain pedal, pitch bends and program changes — and show them on a piano and in a log. Nothing is sent anywhere; it all happens on your device.
Access is only requested when you click, and if your browser does not support MIDI the page still explains what is happening and what you can do.
02How to use it
- Connect your MIDI device by USB or through a MIDI interface.
- Press the grant-access button and allow MIDI access.
- Confirm your device appears in the inputs list.
- Play notes, move controls, or press the sustain pedal and watch the events appear.
- Use the log’s filter, clear and download options to inspect the message stream.
03What this test covers
What it detects
- Connected MIDI inputs and outputs and their connection state
- Note on/off events with velocity and channel
- Control changes (including sustain), pitch bend and program changes
- Manufacturer and device name where the browser provides them
What it can’t detect
- Anything on browsers without Web MIDI (notably Safari and Firefox have limited or no support)
- A device already held open exclusively by another application
- Audio — MIDI carries performance data, not sound
04Troubleshooting
| Symptom | What to do |
|---|---|
| Unsupported browser | Use Chrome or Edge over HTTPS; Safari and Firefox currently have limited or no Web MIDI support. |
| No device shown | Reconnect the device and make sure no DAW or other app is holding it open, then reload. |
| Permission not granted | Allow MIDI access when prompted, or reset the permission in your browser’s site settings. |
| Notes but no sustain | Make sure your sustain pedal is working; some pedals need to be plugged in before you power on the keyboard. |
05FAQ
Which browsers support Web MIDI?
Chrome and Edge on desktop and Android. Safari and Firefox currently have limited or no support.
Why is no device shown?
Make sure it’s connected and not held open by another app (like a DAW), then reconnect.
Is my playing data sent anywhere?
No. MIDI messages are handled locally and never uploaded.
Do I need drivers?
Most class-compliant USB MIDI devices work without extra drivers; some interfaces provide their own.
Can I test both a keyboard and a controller?
Yes — all connected inputs are listed and their messages appear together in the log.
Does this make sound?
No. MIDI carries note and control data; you’d route it to a synth or DAW to hear it.