Online MIDI tester
Test MIDI keys, pads, knobs and pedals directly in a compatible browser.
Start testerWhat can the MIDI tester check?
ACC64 reads messages your controller actually sends to the browser. Check Note On/Off, note number and name, MIDI channel and velocity. The 88-key keyboard makes it easy to verify that physical keys send the expected notes.
Dedicated panels display Control Change, pitch bend, modulation, sustain, Program Change and aftertouch when your hardware sends them. An empty field means no such message has been received; it is not automatically a hardware fault.
How to test a MIDI keyboard step by step
Connect the controller, open the tester in a compatible browser and choose Connect MIDI device. Grant permission, then press every key from low to high while comparing the on-screen keyboard, note name and velocity.
Next test pads, knobs, faders, pitch bend, mod wheel and sustain. Watch CC numbers and their 0–127 values. The event log shows message order and can display readable events or raw HEX bytes.
Understanding velocity, CC, pitch bend and sustain
Velocity is carried by Note On and commonly represents how hard a key or pad was struck. ACC64 shows the latest value plus minimum, maximum and average values received during the current session.
Control Change is commonly used by knobs, faders, wheels and pedals. Mod wheel is typically CC1 and sustain CC64. Pitch bend uses a 14-bit message. Aftertouch is displayed only if the controller actually transmits it.
What if the MIDI controller is not detected?
Check the cable, USB port and whether the operating system sees the device. Close a DAW if it has exclusive access, reload the page and grant MIDI permission again. Trying another USB port and a current desktop Chrome or Edge browser can also help.
If the device is listed but one control produces no event, compare it with controls that work. ACC64 does not simulate missing messages, so an absent Note On, CC or aftertouch event simply means that message did not reach the page.
Privacy and test reliability
The test runs in your browser and displays messages received through Web MIDI API. ACC64 does not invent notes, velocity or controller values, making it useful for quick checks before configuring a DAW.
It cannot replace electronic service diagnostics, but it can help separate a physical control problem from MIDI mapping, connection or music-software configuration issues.
FAQ
How does the online MIDI tester work?
After permission is granted, the browser receives messages from connected MIDI inputs and ACC64 displays their actual values.
Do I need to install software or drivers?
The tester itself needs no installation. Some devices may still require a manufacturer driver so the operating system can expose them correctly.
Does it work with MIDI keyboards, pads and controllers?
Yes, when the device exposes a standard MIDI input available to the browser.
How do I check every keyboard key?
Press the keys one by one and watch the virtual keyboard and Note On/Off log. A working key should send its corresponding note.
How can I test velocity?
Play the same key or pad at different strengths. A velocity-sensitive device should send different Note On velocity values.
Why is velocity always 127?
Some devices or modes transmit fixed velocity. ACC64 displays the received value without correcting it.
How do I test pitch bend, mod wheel and sustain?
Move the pitch and modulation controls and press sustain. The tester shows pitch bend, CC1 and CC64 when those messages are transmitted.
Why does Aftertouch or Program Change show a dash?
No such message has been received in the current session. Not every controller supports or sends these message types.
Can I test MIDI knobs and faders?
Yes. Move them and watch Control Change for the CC number and its 0–127 value.
Does ACC64 create demo values without a device?
No. Fields remain empty or show a dash until real MIDI messages are received.