Uno vs Nano vs Mega: Which Board for Which Project
Arduino Uno
The default reference board — ATmega328P, 14 digital pins (6 PWM), 6 analog inputs, 32KB flash. Pick this when you're learning, following tutorials (most assume Uno pinouts), or need the widest shield compatibility. Full-size USB-B, breadboard-unfriendly footprint though.
Arduino Nano
Same ATmega328P chip as the Uno, same specs, but breadboard-friendly DIP footprint and a Mini/Micro USB connector. Pick this for anything you're prototyping directly on a breadboard, or a permanent project where you want a smaller footprint than the Uno's full-size board. Functionally identical code compatibility to Uno — same chip, same pin count, just repackaged.
Arduino Mega 2560
ATmega2560 — 54 digital pins (15 PWM), 16 analog inputs, 256KB flash, 4 hardware serial ports (vs Uno/Nano's 1). Pick this when you genuinely run out of pins on a Uno/Nano — large robotics builds with many servos/sensors, CNC controllers (GRBL's more elaborate builds), multi-serial-device projects (talking to a GPS module and a Bluetooth module and a debug console simultaneously, each needing its own hardware UART).
Quick Decision Table
- Learning/tutorials: Uno
- Breadboard prototyping, permanent small project: Nano
- Need >20 I/O pins or multiple hardware serial ports: Mega
- Need WiFi/Bluetooth built in: none of these — look at an ESP32 dev board instead (different architecture, but Arduino-IDE-compatible)
A Note on Clones
Genuine Arduino boards cost more than clones for the same ATmega chip — clones work fine for 95% of projects, the main risk is inconsistent USB-serial chip quality (see the IDE setup guide's driver section) and occasionally looser manufacturing tolerances on pin headers. For anything you're actually shipping/selling, genuine boards or well-reviewed clones are worth the premium; for personal projects, clones are usually fine.