Arduino IDE 2.3.7 baud rate selection missing

Development Tools IDE 2.x
1

Hello everyone,

the Arduino IDE isn’t showing the baud rate dropdown list. I’ve tried running it as an administrator, reinstalling it, and allowing Controlled Folder Access, but the option is still missing.

Does anyone know how to fix this issue?

Below is the relevant section from the startup debug:

2026-02-08T17:19:57.426Z monitor-service INFO started monitor to COM6 using serial2026-02-08T17:19:57.429Z root ERROR Uncaught Exception:  Error: EPERM: operation not permitted, open 'c:\Users\tm\.arduinoIDE\pluggable-monitor-settings.json'2026-02-08T17:19:57.429Z root ERROR Error: EPERM: operation not permitted, open 'c:\Users\tm\.arduinoIDE\pluggable-monitor-settings.json'

Best

Adam

Screenshot 2026-02-08 183325
Screenshot 2026-02-08 183325665×407 10.3 KB

2

Hi @nebulae.

It might be that the ownership of the pluggable-monitor-settings.json file somehow ended up being changed, causing your normal user account to no longer be able to access the file.

Arduino IDE will automatically generate this file if it doesn't exist, so the most simple solution will be to delete the file and then allow Arduino IDE to generate a fresh file. The new file will have the correct ownership settings for Arduino IDE to be able to access it.

Try this:

  1. Close all Arduino IDE windows if it is running.
  2. Start Windows "File Explorer".
  3. Navigate to the c:\Users\tm\.arduinoIDE folder
  4. Delete the pluggable-monitor-settings.json file you see in that folder.

Now start Arduino IDE again. Hopefully Serial Monitor will now work as expected.

Arduino IDE stores the Serial Monitor settings like the baud rate and line ending menu selections in the pluggable-monitor-settings.json file. It configures Serial Monitor according to those saved settings the next time you open the port in Serial Monitor. So this is a convenience feature, but there is no irreplaceable data stored in this file. You only need to remember to select the appropriate items from the Serial Monitor menus.

3

Hi @ptillisch thank you for your response.

I tried removing the .json file, but it didn’t help. The Arduino IDE recreates the file, but the baud rate option still doesn’t show up.

4

Do you still see that "EPERM: operation not permitted" error in the startup debug output if you start Arduino IDE from the PowerShell terminal as you did before?

5

I deleted the .json file, started the IDE in debug mode, and then powered up the ESP32 board. Here’s the log:

2026-02-08T19:17:40.220Z discovery-log INFO {"eventType":"add","port":{"matchingBoardsList":[],"port":{"address":"COM6","label":"COM6","protocol":"serial","protocolLabel":"Serial Port (USB)","propertiesMap":[["pid","0xEA60"],["serialNumber","01BADC5C"],["vid","0x10C4"]],"hardwareId":"01BADC5C"}},"error":""}
2026-02-08T19:17:40.477Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Starting monitor process" monitor=serial-monitor
2026-02-08T19:17:40.486Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Monitor process started successfully!" monitor=serial-monitor
2026-02-08T19:17:40.486Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="HELLO 1 \"arduino-cli 1.3.1\"" monitor=serial-monitor
2026-02-08T19:17:40.555Z monitor-service INFO starting monitor
2026-02-08T19:17:40.589Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Starting monitor process" monitor=serial-monitor
2026-02-08T19:17:40.606Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Monitor process started successfully!" monitor=serial-monitor
2026-02-08T19:17:40.607Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="HELLO 1 \"arduino-cli 1.3.1\"" monitor=serial-monitor
2026-02-08T19:17:40.644Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=hello message=OK monitor=serial-monitor
2026-02-08T19:17:40.644Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=hello message=OK monitor=serial-monitor
2026-02-08T19:17:40.644Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command=DESCRIBE monitor=serial-monitor
2026-02-08T19:17:40.645Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command=DESCRIBE monitor=serial-monitor
2026-02-08T19:17:40.647Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=describe message=OK monitor=serial-monitor
2026-02-08T19:17:40.648Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=describe message=OK monitor=serial-monitor
2026-02-08T19:17:40.650Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command=QUIT monitor=serial-monitor
2026-02-08T19:17:40.650Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command=QUIT monitor=serial-monitor
2026-02-08T19:17:40.651Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=quit message=OK monitor=serial-monitor
2026-02-08T19:17:40.654Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=quit message=OK monitor=serial-monitor
2026-02-08T19:17:40.658Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Killing monitor process" monitor=serial-monitor
2026-02-08T19:17:40.658Z daemon INFO time="2026-02-08T20:17:40+01:00" level=error msg="stopped decode loop: EOF" monitor=serial-monitor
2026-02-08T19:17:40.658Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Killing monitor process" monitor=serial-monitor
2026-02-08T19:17:40.661Z daemon INFO time="2026-02-08T20:17:40+01:00" level=error msg="stopped decode loop: EOF" monitor=serial-monitor
2026-02-08T19:17:40.673Z daemon INFO time="2026-02-08T20:17:40+01:00" level=error msg="Sent kill signal" error="Access is denied." monitor=serial-monitor
2026-02-08T19:17:40.673Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Monitor process killed" monitor=serial-monitor
2026-02-08T19:17:40.684Z daemon INFO time="2026-02-08T20:17:40+01:00" level=error msg="Sent kill signal" error="Access is denied." monitor=serial-monitor
time="2026-02-08T20:17:40+01:00" level=info msg="Monitor process killed" monitor=serial-monitor
2026-02-08T19:17:40.693Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Starting monitor process" monitor=serial-monitor
2026-02-08T19:17:40.706Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Monitor process started successfully!" monitor=serial-monitor
time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="HELLO 1 \"arduino-cli 1.3.1\"" monitor=serial-monitor
2026-02-08T19:17:40.723Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=hello message=OK monitor=serial-monitor
2026-02-08T19:17:40.723Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command=DESCRIBE monitor=serial-monitor
2026-02-08T19:17:40.724Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=describe message=OK monitor=serial-monitor
2026-02-08T19:17:40.724Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="CONFIGURE baudrate 9600" monitor=serial-monitor
2026-02-08T19:17:40.724Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=configure message=OK monitor=serial-monitor
2026-02-08T19:17:40.725Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="CONFIGURE bits 8" monitor=serial-monitor
2026-02-08T19:17:40.725Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=configure message=OK monitor=serial-monitor
2026-02-08T19:17:40.725Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="CONFIGURE dtr off" monitor=serial-monitor
2026-02-08T19:17:40.726Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=configure message=OK monitor=serial-monitor
2026-02-08T19:17:40.727Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="CONFIGURE parity none" monitor=serial-monitor
2026-02-08T19:17:40.727Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=configure message=OK monitor=serial-monitor
2026-02-08T19:17:40.727Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="CONFIGURE rts off" monitor=serial-monitor
2026-02-08T19:17:40.730Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=configure message=OK monitor=serial-monitor
2026-02-08T19:17:40.733Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="CONFIGURE stop_bits 1" monitor=serial-monitor
2026-02-08T19:17:40.734Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=configure message=OK monitor=serial-monitor
2026-02-08T19:17:40.734Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="sending command" command="OPEN 127.0.0.1:61158 COM6" monitor=serial-monitor
2026-02-08T19:17:40.739Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="received message" error=false event_type=open message=OK monitor=serial-monitor
2026-02-08T19:17:40.739Z daemon INFO time="2026-02-08T20:17:40+01:00" level=info msg="Port COM6 successfully opened"
2026-02-08T19:17:40.741Z monitor-service INFO Using port configuration for serial:COM6: {"settingsList":[{"settingId":"baudrate","value":"9600"},{"settingId":"bits","value":"8"},{"settingId":"dtr","value":"off"},{"settingId":"parity","value":"none"},{"settingId":"rts","value":"off"},{"settingId":"stop_bits","value":"1"}]}
2026-02-08T19:17:40.741Z monitor-service INFO started monitor to COM6 using serial
2026-02-08T19:17:40.743Z root ERROR Uncaught Exception:  Error: EPERM: operation not permitted, open 'c:\Users\tm\.arduinoIDE\pluggable-monitor-settings.json'
2026-02-08T19:17:40.743Z root ERROR Error: EPERM: operation not permitted, open 'c:\Users\tm\.arduinoIDE\pluggable-monitor-settings.json'

Despite the error, the baud rate selection is now available.

image

However, it doesn’t let me change the baud rate.

Very strange.