CircuiteraChoose the correct bootloader
The new Nano bootloader profile uploads at 115200 baud; the old profile uses 57600 baud. Select the profile that matches the bootloader actually installed on your board. If the sketch verifies but the bootloader handshake fails, check this setting along with the cable and port. Changing the profile does not install a different bootloader.
Use Nano-specific analog inputs
The Nano variant includes A0–A7. A6 and A7 are analog-input-only: do not treat them as ordinary digital outputs. I2C uses A4/A5, and PWM follows the ATmega328P pin assignments on D3, D5, D6, D9, D10, and D11. Pin helpers and autocomplete follow the selected board, so select Nano before relying on those hints.
Keep the sketch within memory
Both classic Nano profiles compile for ATmega328P at 16 MHz and provide 30,720 bytes of application flash and 2,048 bytes of SRAM. Large display buffers or long text strings can consume SRAM quickly. Read the build’s static RAM report and leave room for runtime stack and heap use; a successful link does not guarantee that an oversized program will run reliably.
Understand which Nano this covers
Nano Every, Nano 33, and Nano ESP32 are different targets and cannot use this profile. Some classic clones have USB bridges that need host drivers or school administrator approval. Use Serial Monitor to check a simple known-working sketch after upload. The browser cannot bypass operating-system or managed-device restrictions.