![COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center](https://support.arduino.cc/hc/article_attachments/360016539239/COM_port_changes_7.png)
COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center
![COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center](https://support.arduino.cc/hc/article_attachments/360016532060/COM_port_changes_4.png)
COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center
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Arduino Nano - "avrdude: ser_open():system can't open device "\\.\COM1": the system cannot find the file specified" - Stack Overflow
![COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center](https://support.arduino.cc/hc/article_attachments/360016531980/COM_port_changes_3.png)
COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center
![Can't open device "\\.\COM4": Access is denied error when uploading a sketch from Arduino IDE | I learned it. I share it. Can't open device "\\.\COM4": Access is denied error when uploading a sketch from Arduino IDE | I learned it. I share it.](https://gyorgybalassy.files.wordpress.com/2020/10/arduino-port-selection.png)
Can't open device "\\.\COM4": Access is denied error when uploading a sketch from Arduino IDE | I learned it. I share it.
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Change USB COM port description of the "Arduino UNO R3" [SOLVED] - Programming Questions - Arduino Forum
![COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center COM port number changes when connecting board on different ports or in bootloader mode – Arduino Help Center](https://support.arduino.cc/hc/article_attachments/360016539219/COM_port_changes_5.png)