MIDI tester — test your MIDI keyboard & controller input online

What is a MIDI tester?

A MIDI tester (also called a MIDI test or MIDI input test) checks that a MIDI device is recognized by your computer and that its input messages arrive correctly. When you plug in a MIDI keyboard, pad controller, or MIDI interface, this online MIDI tester lists every connected input and output device and shows each incoming message live: which notes you pressed and how hard (velocity), sustain and other control changes (CC), and pitch-bend movements. It is the fastest way to confirm a MIDI input keyboard works before you blame the DAW, the cable, or the drivers. Everything runs in the browser with the Web MIDI API — nothing is recorded, uploaded, or sent to a server.

Online MIDI tester features

A private, browser-based MIDI test tool that enumerates your MIDI devices and shows live input messages as you play.

1. Lists connected MIDI input & output devices: The MIDI tester shows every input and output port the browser can see — name and manufacturer of each MIDI keyboard, pad controller, and interface, with a connected/disconnected state per port.
2. Live note readout with names & velocity: Press a key on your MIDI keyboard and the tester displays the note (for example C4 or A#2), its MIDI number, and the velocity you played. Note-off messages clear the note from the held-notes strip.
3. Control change (CC) monitoring: Move the mod wheel, press the sustain pedal, or turn any knob: the tester names common controllers (Mod wheel, Volume, Pan, Sustain, Expression, and more) and shows the raw CC number and value.
4. Pitch bend, program, and aftertouch readout: Bend the wheel and the tester reports pitch-bend direction and amount. Program-change and aftertouch messages are shown too, so the full MIDI input keyboard message set is visible.
5. Timestamped event log: Every received message is added to a scrolling log with a per-session timestamp, so you can replay what your MIDI controller sent — useful when debugging flaky cables or drivers.
6. USB & Bluetooth MIDI, fully local: Works with MIDI over USB, Bluetooth LE MIDI, and MIDI interfaces exposed to the browser. Input is processed locally with the Web MIDI API — no data is recorded or uploaded.

How to test a MIDI keyboard online

A three-step MIDI test to confirm your device is detected and that its input registers correctly.

1. Connect and switch on your MIDI device: Plug the MIDI keyboard, pad controller, or interface into USB (or pair it over Bluetooth LE MIDI) and power it on. Make sure the operating system sees the device before you test.
2. Click "Start MIDI test" and allow access: This MIDI tester runs on the Web MIDI API, so the browser will ask for permission to access your MIDI devices. Grant it — access is local and never leaves your computer.
3. Play notes and move controls, then read the events: Press keys, hold the sustain pedal, move the mod wheel, and bend pitch. Each action should appear instantly in the readout and event log. If nothing appears, work through the troubleshooting steps below.

MIDI troubleshooting — why no input shows up

Common fixes when a MIDI keyboard is connected but the MIDI test shows no device or no incoming messages.

1. Use a supporting browser: The Web MIDI API works in Chrome, Edge, Opera, and Samsung Internet. Firefox 108+ supports it but needs a one-time site-permission add-on. Safari and iOS do not support it — use Chrome for the MIDI test.
2. Check the OS sees the device first: On Windows, check Device Manager for the keyboard or "USB Audio Device"; on macOS check Audio MIDI Setup. If the OS does not list the device, the browser cannot see it either — try another cable or USB port.
3. The device appears but no notes register: Some controllers need their output enabled or the right "MIDI out" port selected in their editor software. Bluetooth MIDI devices may also disconnect when idle — wake and re-pair them, then retest.
4. Notes show in the tester but not in my DAW: That means the keyboard and cable are fine — the DAW just has the wrong MIDI input selected or the track is not armed. Enable the MIDI track input and record-arm in your DAW.
5. Stuck notes after unplugging or a crash: If a note stays lit in software, send All Notes Off (CC 123) or power-cycle the keyboard. This MIDI tester clears its held-notes display when a Note Off arrives.
6. Bluetooth MIDI latency or dropouts: Bluetooth MIDI adds a few milliseconds and can stutter near other 2.4 GHz traffic. For the cleanest MIDI test and lowest latency, connect over USB instead.

Sources & References

Authoritative references for the Web MIDI API used to enumerate devices and receive input messages in this MIDI tester.

• Web MIDI API — accessing MIDI devices from the browser

  “The Web MIDI API is a Web API that enables web applications to enumerate and communicate with MIDI devices connected to the computer.”

  This MIDI tester calls navigator.requestMIDIAccess() to list inputs and outputs and to attach a handler that receives MIDI messages from your keyboard and controller. developer.mozilla.org/en-US/docs/Web/API/Web_MIDI_API

• MIDIMessageEvent — the raw bytes behind each message

  “The MIDIMessageEvent interface of the Web MIDI API represents the event passed to the onmidimessage event handler of the MIDIInput interface.”

  Each incoming event exposes a data buffer whose status byte is decoded here into note on/off, control change, pitch bend, or program change messages with their channel and values. developer.mozilla.org/en-US/docs/Web/API/MIDIMessageEvent

Frequently Asked Questions

Have questions? We have answers.

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