MIDI control-change numbers changed? How to recheck

You switched browsers and now a knob seems to send a different MIDI control-change number. Before changing your controller settings, check that both browsers are reading the same device and the same control.

The MIDI Test shows incoming MIDI messages, including the control-change number and value. Compare the same knob in each browser to see whether the message changed or you are looking at a different input or display.

Recheck the control-change number

1. Open the MIDI Test in a browser that supports MIDI access. If the browser asks for permission to use MIDI devices, allow it. Safari does not support this test, so use a different browser if you switched to Safari.
2. If the test shows more than one MIDI input, choose the same controller input you used before. Similar or identical names can refer to separate ports or virtual devices.
3. Turn one physical knob slowly from its minimum to its maximum. Watch the incoming messages and note the control-change number, channel, and values you see.
4. Open the test in the other browser and repeat with the same controller, input, knob, and movement. Keep the controller's preset and any connected MIDI software unchanged.
5. Compare the control-change number, not just the changing value. A useful note might look like: knob A, CC 21, channel 1, values 0 to 127.

A control-change message contains a controller number and a value. The number identifies the control assignment, while the value changes as you move a knob, pedal, or slider. Standard MIDI control-change numbers and values range from 0 to 127.

What the result means

The number stays the same while the value changes

This is the normal result for one control. For example, the knob may keep sending CC 21 while its values rise from 18 to 90 as you turn it. The browser switch did not change the assignment.

The number differs between browsers

First check whether both tests are receiving messages from the same MIDI input. A controller can expose more than one port, and MIDI routing software can provide virtual inputs with different names. If the input is definitely the same, check the controller's preset or mapping. A browser normally displays the message it receives, rather than assigning a new CC number to the knob.

No messages appear in one browser

The browser may not support MIDI access, may not have permission, or may be listening to a different input. If you switched to Safari, the MIDI Test will not work there. You can read more about that limitation in why browser MIDI testing does not work in Safari.

One movement produces several messages

Some controllers send more than one message for a control. A high-resolution control may use a pair of related CC numbers, or a knob may send additional messages for its mode or bank. Compare the full set of messages and values, not just the first number shown.

The values jump or move in the opposite direction

This does not necessarily mean the CC number changed. A controller can send values in larger steps, reverse the direction, or use a different preset. Compare the number first, then consider the value pattern separately.

How to fix a mismatch

1. Check the browser's MIDI permission. If access was denied, open the browser's site controls beside the address bar, allow MIDI device access if that option is shown, then reload the test. Permission names and controls vary by browser.
2. Choose the same input in both tests. If several devices or ports appear, select the physical controller's input rather than a similarly named output or virtual port. Disconnect other MIDI devices temporarily if you are unsure which one is sending messages.
3. Close MIDI routing or remapping software. A DAW, virtual MIDI router, or controller utility may expose a transformed stream under a separate input name. Close it for a direct comparison, or make sure both browsers use the same routed input.
4. Check the controller preset. A preset can assign the knob to a different CC number. Compare the controller's saved setup with the one you used before switching browsers. Save or photograph your current preset before restoring a default.
5. Reconnect the controller. Unplug a USB controller and reconnect it, then reload the test and select its input again. For a Bluetooth controller, check the connection in Windows 11 under Settings › Bluetooth & devices › Devices, or on a Mac under System Settings › Bluetooth.
6. Compare with a known control. Test another knob or pedal on the same controller. If only one control sends a different number, its mapping or preset is the likely cause. If all controls differ, check that you have not selected a different device profile or virtual input.

Why the browser switch can look like a mapping change

Browsers can differ in which MIDI features they support and how they list connected devices. They can also retain different site permissions. Those differences may change whether the test can access the controller or which input you select, but they do not usually rewrite a control-change number sent by the hardware.

Some controllers have multiple operating modes, presets, or ports. A knob might send one CC number in a general-purpose preset and another in a software-specific preset. If the number differs consistently in both browsers after you confirm the input, the controller setup is a better place to investigate than the browser.

For a clean comparison, write down the controller name, selected input, CC number, channel, and lowest and highest values for each browser.