Fix “Board at COM5 is not available” in Arduino IDE
The IDE is set to a COM port that no longer exists. Re-select the port after replugging; if none appears, it's the cable, driver or a board that keeps resetting.
Community draft — report a mistake
What you see
Board at COM5 is not availableBoard at COM5 is not available
The Arduino IDE remembers the last port you picked. When that port no longer exists because the board was unplugged, renumbered or is mid-reset, the IDE tells you it isn’t available.
Re-select the port. If the board’s port doesn’t appear at all, the problem is the cable, driver or the board itself.
Quick fix — try in order
- 1
Re-select the port
Tools → Port → pick the board's current port. Windows can assign a new number when you use another USB socket or after a driver update.
- 2
Find it by unplugging
Open Tools → Port, unplug the board, note which entry disappears, plug it in again and select that one.
- 3
No port at all? Fix cable or driver
See COM port not showing — charge-only cables and missing CH340/CP2102 drivers are the usual reasons.
- 4
Port comes and goes? The board is resetting
A short circuit, a motor on the 5 V pin, or a native-USB board in a crash loop makes the port vanish repeatedly. Remove attachments and test bare.
Why it happens
When does this appear?
Usually when you open Serial Monitor or start an upload while the selected port is missing — for example after unplugging the board, sleeping the laptop, or switching USB sockets.
Leonardo, Micro, Pro Micro
These have one COM number for the sketch and another for the bootloader. If the sketch crashed USB, the sketch's port is gone; double-tap RESET to get the bootloader port.
Board-specific notes
ESP32-C3 / S3: After an upload through native USB, the port may come back with a different number. Re-select it before opening the monitor.
Drivers — official sources only
Did this fix it?
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