Arduino Development Environment

The Arduino development environment contains a text editor for writing code, a message area, a text console, a toolbar with buttons for common functions, and a series of menus. It connects to the Arduino hardware to upload programs and communicate with them.

Software written using Arduino are called sketches. These sketches are written in the text editor. It has features for cutting/pasting and for searching/replacing text. The message area gives feedback while saving and exporting and also displays errors. The console displays text output by the Arduino environment including complete error messages and other information. The toolbar buttons allow you to verify and upload programs, create, open, and save sketches, and open the serial monitor:

Checks your code for errors.

Stops the serial monitor, or unhighlight other buttons.

Creates a new sketch.

Presents a menu of all the sketches in your sketchbook. Clicking one will open it within the current window.

Note: due to a bug in Java, this menu doesn't scroll; if you need to open a sketch late in the list, use the File | Sketchbook menu instead.

Saves your sketch.

Upload to I/O Board
Compiles your code and uploads it to the Arduino I/O board. See uploading below for details.

Serial Monitor
Opens the serial monitor.

Additional commands are found within the five menus: File, Edit, Sketch, Tools, Help. The menus are context sensitive which means only those items relevant to the work currently being carried out are available.


  • Copy for Discourse
    Copies the code of your sketch to the clipboard in a forum suitable for posting to the forum, complete with syntax coloring.

  • Copy as HTML
    Copies the code of your sketch to the clipboard as HTML, suitable for embedding in web pages.


  • Verify/Compile
    Checks your sketch for errors.

  • Import Library
    Adds a library to your sketch by inserting #include statements at the code of your code. For more details, see libraries below.

  • Show Sketch Folder
    Opens the sketch folder on the desktop.

  • Add File...
    Adds a source file to the sketch (it will be copied from its current location). The new file appears in a new tab in the sketch window. Files can be removed from the sketch using the tab menu.


  • Auto Format
    This formats your code nicely: i.e. indents it so that opening and closing curly braces line up, and that the statements instead curly braces are indented more.

  • Board
    Select the board that you're using. See below for descriptions of the various boards.

  • Serial Port
    This menu contains all the serial devices (real or virtual) on your machine. It should automatically refresh every time you open the top-level tools menu.

  • Burn Bootloader
    The items in this menu allow you to burn a bootloader onto the microcontroller on an Arduino board. This is not required for normal use of an Arduino board but is useful if you purchase a new ATmega (which normally come without a bootloader). Ensure that you've selected the correct board from the Boards menu before burning the bootloader. When using an AVR ISP, you'll need to select the item corresponding to your programmer from the Serial Port menu.


The Arduino environment includes the concept of a sketchbook: a standard place to store your programs (or sketches). The sketches in your sketchbook can be opened from the File > Sketchbook menu or from the Open button on the toolbar. The first time you run the Arduino software, it will automatically create a directory for your sketchbook. You can view or change the location of the sketchbook location from with the Preferences dialog.

Tabs, Multiple Files, and Compilation

A sketch can contain multiple files (tabs). To manage them, click on the right-facing arrow just above the scroll bar near the top of the environment. Tabs have one of four extensions: no extension, .c, .cpp, or .h (if you provide any other extension, the period will be converted to an underscore). Tabs with no extension are treated as parts of a single C++ source file. They, along with any .c or .cpp files in the sketch, are linked together when the sketch is compiled (verified) or built for uploading. Any .h (header files) in the sketch must be explicitly #included.


Before uploading your sketch, you need to select the correct items from the Tools > Board and Tools > Serial Port menus. The boards are described below. On the Mac, the serial port is probably something like /dev/tty.usbserial-1B1 (for a USB board), or /dev/tty.USA19QW1b1P1.1 (for a serial board connected with a Keyspan USB-to-Serial adapter). On Windows, it's probably COM1 or COM2 (for a serial board) or COM4, COM5, COM7, or higher (for a USB board) - to find out, you look for USB serial device in the ports section of the Windows Device Manager. On Linux, it should be /dev/ttyUSB0, /dev/ttyUSB1 or similar.

Once you've selected the correct serial port and board, press the upload button in the toolbar or select the Upload to I/O Board item from the File menu. Current Arduino boards will reset automatically and begin the upload. With older boards that lack auto-reset, you'll need to press the reset button on the board just before starting the upload. On most boards, you'll see the RX and TX LEDs blink as the sketch is uploaded. The Arduino environment will display a message when the upload is complete, or show an error.

When you upload a sketch, you're using the Arduino bootloader, a small program that has been loaded on to the microcontroller on your board. It allows you to upload code without using any additional hardware. The bootloader is active for a few seconds when the board resets; then it starts whichever sketch was most recently uploaded to the microcontroller. The bootloader will blink the on-board (pin 13) LED when it starts (i.e. when the board resets).


Libraries provide extra functionality for use in sketches, e.g. working with hardware or manipulating data. To use a library in a sketch, select it from the Sketch > Import Library menu. This will insert one or more #include statements at the top of the sketch and compile the library with your sketch. Because libraries are uploaded to the board with your sketch, they increase the amount of space it takes up. If a sketch no longer needs a library, simply delete its #include statements from the top of your code.

There is a list of libraries in the reference. Some libraries are included with the Arduino software. Others can be downloaded from a variety of sources. To install these third-party libraries, create a directory called libraries within your sketchbook directory. Then unzip the library there. For example, to install the DateTime library, its files should be in the /libraries/DateTime sub-folder of your sketchbook folder.

Third-Party Hardware

While the Arduino software comes with support for only the official Arduino hardware, support for other hardware can be installed separately. Download the folder containing another platform's files and place it in the hardware sub-folder of the sketchbook folder. Upon restarting the Arduino software, the platform's boards should appear in the Tools > Boards menu. Select the appropriate entry to compile and upload sketches for that board (or to burn bootloaders to it).

Serial Monitor

Displays serial data being sent from the Arduino board (USB or serial board). To send data to the board, enter text and click on the "send" button or press enter. Choose the baud rate from the drop-down that matches the rate passed to Serial.begin in your sketch. Note that on Mac or Linux, the Arduino board will reset (rerun your sketch from the beginning) when you connect with the serial monitor.

You can also talk to the board from Processing, Flash, MaxMSP, etc (see the interfacing page for details).


Some preferences can be set in the preferences dialog (found under the Arduino menu on the Mac, or File on Windows and Linux). The rest can be found in the preferences file, whose location is shown in the preference dialog.


The board selection has two effects: the parameters (e.g. CPU speed and baud rate) used when compiling and uploading sketches; and the file and fuse settings used by the burn bootloader command. Some of the board definitions differ only in the latter, so even if you've been uploading successfully with a particular selection you'll want to check it before burning the bootloader.

  • Arduino Duemilanove or Nano w/ ATmega328
    An ATmega328 running at 16 MHz with auto-reset. Also used for the 16 MHz (5V) versions of the Arduino Pro or Pro Mini with an ATmega328.

  • Arduino Diecimila, Duemilanove, or Nano w/ ATmega168
    An ATmega168 running at 16 MHz with auto-reset. Compilation and upload is equivalent to Arduino NG or older w/ ATmega168, but the bootloader burned has a faster timeout (and blinks the pin 13 LED only once on reset). Also used for the 16 MHz (5V) versions of the Arduino Pro and Pro Mini with an ATmega168.

  • Arduino Mega
    An ATmega1280 running at 16 MHz with auto-reset.

  • Arduino Mini
    Equivalent to Arduino NG or older w/ ATmega168 (i.e. an ATmega168 running at 16 MHz without auto-reset).

  • Arduino BT
    ATmega168 running at 16 MHz. The bootloader burned includes codes to initialize the on-board bluetooth module.

  • LilyPad Arduino w/ ATmega328
    An ATmega328 running at 8 MHz (3.3V) with auto-reset. Equivalent to Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega328.

  • LilyPad Arduino w/ ATmega168
    An ATmega168 running at 8 MHz. Compilation and upload is equivalent to the Arduino Pro or Pro Mini (8 MHz) w/ ATmega168. The bootloader burned, however, has a slower timeout (and blinks the pin 13 LED three times on reset) because the original versions of the LilyPad didn't support auto-reset. They also didn't include an external clock, so the burn bootloader command configures the fuses of ATmega168 for an internal 8 MHz clock.

    If you have a recent version of the LilyPad, (w/ a 6-pin programming header), you'll want to select Arduino Pro or Pro Mini (8 MHz) w/ ATmega168 before burning the bootloader.

  • Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega328
    An ATmega328 running at 8 MHz (3.3V) with auto-reset. Equivalent to LilyPad Arduino w/ ATmega328.

  • Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega168
    An ATmega168 running at 8 MHz (3.3V) with auto-reset.

  • Arduino NG or older w/ ATmega168
    An ATmega168 running at 16 MHz without auto-reset. Compilation and upload is equivalent to Arduino Diecimila or Duemilanove w/ ATmega168, but the bootloader burned has a slower timeout (and blinks the pin 13 LED three times on reset).

  • Arduino NG or older w/ ATmega8
    An ATmega8 running at 16 MHz without auto-reset.

The text of the Arduino getting started guide is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the guide are released into the public domain.