Windows 11 Serial Device Management

COM port utilities

programming Arduino devices uses, then abandons, COMn names,
... which Windows continues to consider "in use".

COM port renaming

Device Manager can rename active COM devices,
but in Windows 11 does not support removing "in use" COM ports
by set DEVMGR_SHOW_NONPRESENT_DEVICES=1 with View > Show hidden devices

ComNameArbiterTool

Frees "in use" COM ports without Registry Editor fiddling

PuTTY

Popular terminal emulator

com0com virtual null modem signed drivers

Modern Windows wants signed drivers...

How to PDF   Run as admin:  setupc.exe

Enter 'help' to get info about usage of Setup for com0com.

command> list
       CNCA0 PortName=COM18,PlugInMode=no,cts=ldtr
       CNCB0 PortName=COM2,EmuOverrun=yes,ExclusiveMode=no,cts=on,dsr=on,dcd=on
command> change CNCA0 PortName=COM8
       CNCA0 PortName=COM18,PlugInMode=no,cts=ldtr
change CNCA0 PortName=COM8,PlugInMode=no,cts=ldtr
Restarted CNCA0 com0com\port \Device\com0com10
       CNCB0 PortName=COM2,EmuOverrun=yes,ExclusiveMode=no,cts=on,dsr=on,dcd=on
ComDB: COM8 - logged as "in use"
ComDB: COM18 - released
command> quit

mode.com

traditional command line binary that lists ports, e.g.:
R:\Temp>mode.com