How to test a MIDI device
- Connect the device with USB, or through a MIDI interface.
- Press Connect MIDI devices and allow MIDI access if the browser asks.
- Play every key. Each one lights up on the piano and shows its note and velocity.
- Turn every knob and move every fader. Each control shows its CC number and value from 0 to 127.
- Move the pitch wheel and check that it springs back to 0.
Common MIDI problems
- Device not listed: try another USB cable and port, and close music apps that might hold the device exclusively (some Windows drivers allow only one app at a time).
- Some keys always play softly or loudly: uneven velocity usually means worn rubber contacts under those keys.
- A key plays two notes or hangs: look for missing Note off messages in the log.
- Knob values jump: a dirty potentiometer. Turning it fully back and forth a few times can help.
- Notes on the wrong channel: the log shows the channel of every message, so you can match it to your software.
Browser support
Web MIDI works in Chrome, Edge, Opera and Firefox on Windows, macOS, Linux and ChromeOS. Safari and all browsers on iPhone and iPad do not support it.
Frequently asked questions
Short answers to the questions people ask most about this test.
How do I test my MIDI keyboard online?
Connect it with USB, open this page in Chrome, Edge or Firefox, press Connect and play. Every note and control appears live.
Does the MIDI tester work in Safari?
No. Safari does not support Web MIDI. Use Chrome, Edge, Opera or Firefox on a computer.
What is velocity?
Velocity is how hard a key was struck, from 1 to 127. A healthy keyboard gives a smooth range from soft to hard playing.