How to Use Arduino as a Keyboard or Mouse

What is a mouse/keyboard emulator?

A mouse/keyboard emulator on Arduino means the board pretends to be a real USB keyboard or mouse when plugged into a computer.

Instead of sending data over serial like a normal Arduino sketch, the board identifies itself as a USB HID device (Human Interface Device), the same category used by real keyboards and mice. Visit here for more information.

This tutorial is based on the circuit of a simple button with a digital input resistor. Please refer to this tutorial for the wiring.

Arduino HID vs Serial Communication

Feature	HID Emulation	Serial Communication
Purpose	Pretend to be keyboard/mouse	Send data between devices/programs
How PC sees it	Keyboard, mouse, joystick	COM port / serial device
Driver needed	Usually no	Usually USB serial driver
Human input simulation	Yes	No
Can type into apps directly	Yes	No
Can move mouse cursor	Yes	No
Communication type	HID protocol	UART/USB Serial
Typical libraries	Keyboard.h, Mouse.h	Serial.h
Data visibility	Acts as user input	Raw data stream
Best for	Automation/macros/controllers	Sensors/debugging/device communication
Security sensitivity	Higher	Lower
Ease of debugging	Harder	Easier
Works in BIOS/login screen	Often yes	Usually no
Bidirectional communication	Limited	Excellent
Speed for data transfer	Lower	Better for data
Common boards	Leonardo, Micro, UNO R4 series	Almost all Arduino boards

In short, if you only need simple interaction (no raw data and two-way communication) to replace the mundane mouse and keyboard, the HID Emulation is easier to set up and more straightforward to use than serial communication.

Getting started

This code will make every button click into pressing a "w" on the keyboard.

#include <Keyboard.h>
boolean prevBtnState = LOW;

void setup() {
  Keyboard.begin();
  delay(1000);

  pinMode(2, INPUT_PULLUP); // Internal pull-up enabled
  Serial.begin(9600);
}

void loop() {
  int btnState = digitalRead(2);
  if ( btnState == LOW && prevBtnState == HIGH ) {
      Serial.println("1");
      Keyboard.press('w');
      delay(100);
      Keyboard.releaseAll();
      delay(1000); 

  }
  prevBtnState = btnState;
}

After the code is uploaded, you may see a pop-up like this, as your computer now sees the Arduino as an actual keyboard!