Introduced in Arduino IDE 1.6.4, Boards Manager makes it easy to install and update Arduino platforms. In order to provide Boards Manager installation support for a platform, a JSON formatted index file must be published. This is the specification for that file.

Boards Manager functionality is provided by Arduino CLI and Arduino IDE.

Naming of the JSON index file

Many different index files coming from different vendors may be in use, so each vendor should name their own index file in a way that won't conflict with others. The file must be named as follows:

package_YOURNAME_PACKAGENAME_index.json

The prefix package_ and the postfix _index.json are mandatory (otherwise the index file is not recognised by the Arduino development software) while the choice of YOURNAME_PACKAGENAME is left to the packager. We suggest using a domain name owned by the packager. For example:

package_arduino.cc_index.json

or

package_example.com_avr_boards_index.json

The index URL is periodically checked for updates, so expect a constant flow of downloads (proportional to the number of active users).

JSON Index file contents

The root of the JSON index is an array of packages:

{
  "packages": [PACKAGE_XXXX]
}

3rd party vendors should use a single PACKAGE_XXXX that is a dictionary map with the vendor's metadata, a list of PLATFORMS and a list of TOOLS. For example:

    {
      "name": "arduino",
      "maintainer": "Arduino LLC",
      "websiteURL": "http://www.arduino.cc/",
      "email": "packages@arduino.cc",

      "platforms": [PLATFORM_AVR, PLATFORM_ARM, PLATFORM_XXXXX, PLATFORM_YYYYY],

      "tools": [
        TOOLS_COMPILER_AVR,
        TOOLS_UPLOADER_AVR,
        TOOLS_COMPILER_ARM,
        TOOLS_XXXXXXX,
        TOOLS_YYYYYYY
      ]
    }

The metadata fields are:

name: the folder used for the installed cores. The vendor folder name of the installed package is determined by this field
maintainer: the extended name of the vendor that is displayed on the Arduino IDE Boards Manager GUI
websiteURL: the URL to the vendor's website, appears on the Arduino IDE Boards Manager as a "More info" link
email: the email of the vendor/maintainer

Now, before looking at PLATFORMS, let's explore first how TOOLS are made.

Tools definitions

Each tool describes a binary distribution of a command line tool. A tool can be:

a compiler toolchain
an uploader
a file preprocessor
a debugger
a program that performs a firmware upgrade
a pluggable discovery
a pluggable monitor

basically anything that can run on the user's host PC and do something useful.

For example, Arduino uses two command line tools for the AVR boards: avr-gcc (the compiler) and avrdude (the uploader).

Tools are mapped as JSON in this way:

        {
          "name": "avr-gcc",
          "version": "7.3.0-atmel3.6.1-arduino7",
          "systems": [
            {
              "size": "34683056",
              "checksum": "SHA-256:3903553d035da59e33cff9941b857c3cb379cb0638105dfdf69c97f0acc8e7b5",
              "host": "arm-linux-gnueabihf",
              "archiveFileName": "avr-gcc-7.3.0-atmel3.6.1-arduino7-arm-linux-gnueabihf.tar.bz2",
              "url": "http://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-arm-linux-gnueabihf.tar.bz2"
            },
            {
              "size": "38045723",
              "checksum": "SHA-256:03d322b9df6da17289e9e7c6233c34a8535d9c645c19efc772ba19e56914f339",
              "host": "aarch64-linux-gnu",
              "archiveFileName": "avr-gcc-7.3.0-atmel3.6.1-arduino7-aarch64-pc-linux-gnu.tar.bz2",
              "url": "http://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-aarch64-pc-linux-gnu.tar.bz2"
            },
            {
              "size": "36684546",
              "checksum": "SHA-256:f6ed2346953fcf88df223469088633eb86de997fa27ece117fd1ef170d69c1f8",
              "host": "x86_64-apple-darwin14",
              "archiveFileName": "avr-gcc-7.3.0-atmel3.6.1-arduino7-x86_64-apple-darwin14.tar.bz2",
              "url": "http://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-x86_64-apple-darwin14.tar.bz2"
            },
            {
              "size": "52519412",
              "checksum": "SHA-256:a54f64755fff4cb792a1495e5defdd789902a2a3503982e81b898299cf39800e",
              "host": "i686-mingw32",
              "archiveFileName": "avr-gcc-7.3.0-atmel3.6.1-arduino7-i686-w64-mingw32.zip",
              "url": "http://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-i686-w64-mingw32.zip"
            },
            {
              "size": "37176991",
              "checksum": "SHA-256:954bbffb33545bcdcd473af993da2980bf32e8461ff55a18e0eebc7b2ef69a4c",
              "host": "i686-linux-gnu",
              "archiveFileName": "avr-gcc-7.3.0-atmel3.6.1-arduino7-i686-pc-linux-gnu.tar.bz2",
              "url": "http://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-i686-pc-linux-gnu.tar.bz2"
            },
            {
              "size": "37630618",
              "checksum": "SHA-256:bd8c37f6952a2130ac9ee32c53f6a660feb79bee8353c8e289eb60fdcefed91e",
              "host": "x86_64-linux-gnu",
              "archiveFileName": "avr-gcc-7.3.0-atmel3.6.1-arduino7-x86_64-pc-linux-gnu.tar.bz2",
              "url": "http://downloads.arduino.cc/tools/avr-gcc-7.3.0-atmel3.6.1-arduino7-x86_64-pc-linux-gnu.tar.bz2"
            }
          ]
        },

The field name and version are respectively the name and version of the tool. Each tool is uniquely identified by the triple (packager, name, version). packager (AKA "vendor") is defined by the name value of the tool's package. There can be many different versions of the same tool available at the same time, for example:

(arduino, avr-gcc, 5.4.0-atmel3.6.1-arduino2)
(arduino, avr-gcc, 7.3.0-atmel3.6.1-arduino5)
(arduino, avr-gcc, 7.3.0-atmel3.6.1-arduino7)
(arduino, avrdude, 5.11)
(arduino, avrdude, 6.0)
(arduino, avrdude, 6.1)
.....

The systems field lists all available Tools Flavours.

The other fields are:

url: the download URL of the tool's archive
archiveFileName: the name of the file saved to disk after the download (some web servers don't provide the filename through the HTTP request)
size: the size of the archive in bytes
checksum: the checksum of the archive, used to check if the file has been corrupted. The format is ALGORITHM:CHECKSUM, currently MD5, SHA-1,SHA-256 algorithm are supported, we recommend SHA-256. On *nix or macOS you can use the command shasum -a 256 filename to generate SHA-256 checksums. There are free options for Windows, including md5deep. There are also online utilities for generating checksums.

Tools flavours (available builds made for different OS)

Each tool version may come in different build flavours for different OS. Each flavour is listed under the systems array. The IDE will take care to install the right flavour for the user's OS by matching the host value with the following table or fail if a needed flavour is missing.

OS flavour	`host` regexp	suggested `host` value
Linux 32	`i[3456]86-.*linux-gnu`	`i686-linux-gnu`
Linux 64	`x86_64-.*linux-gnu`	`x86_64-linux-gnu`
Linux Arm	`arm.*-linux-gnueabihf`	`arm-linux-gnueabihf`
Linux Arm64	`(aarch64\|arm64)-linux-gnu`	`aarch64-linux-gnu`
Linux RISC-V 64	`riscv64-linux-gnu`	`riscv64-linux-gnu`
Windows 32	`i[3456]86-.*(mingw32\|cygwin)`	`i686-mingw32` or `i686-cygwin`
Windows 64	`(amd64\|x86_64)-.*(mingw32\|cygwin)`	`x86_64-migw32` or `x86_64-cygwin`
MacOSX 32	`i[3456]86-apple-darwin.*`	`i686-apple-darwin`
MacOSX 64	`x86_64-apple-darwin.*`	`x86_64-apple-darwin`
MacOSX Arm64	`arm64-apple-darwin.*`	`arm64-apple-darwin`
FreeBSD 32	`i?[3456]86-freebsd[0-9]*`	`i686-freebsd`
FreeBSD 64	`amd64-freebsd[0-9]*`	`amd64-freebsd`
FreeBSD Arm	`arm.-freebsd[0-9]`	`arm-freebsd`

The host value is matched with the regexp, this means that a more specific value for the host field is allowed (for example you may write x86_64-apple-darwin14.1 for MacOSX instead of the suggested x86_64-apple-darwin), by the way, we recommend to keep it simple and stick to the suggested value in the table.

Some OS allows to run different flavours:

The OS...	...may also run builds for
Windows 64	Windows 32
MacOSX 64	MacOSX 32
MacOSX Arm64	MacOSX 64 or MacOSX 32

This is taken into account when the tools are downloaded (for example if we are on a Windows 64 machine and the needed tool is available only for the Windows 32 flavour, then the Windows 32 flavour will be downloaded and used).

For completeness, the previous example avr-gcc comes with builds for:

ARM Linux 32 (arm-linux-gnueabihf),
ARM Linux 64 (aarch64-linux-gnu),
MacOSX 64 (x86_64-apple-darwin14),
Windows 32 (i686-mingw32),
Linux 32 (i686-linux-gnu),
Linux 64 (x86_64-linux-gnu)
MacOSX Arm64 will use the MacOSX 64 flavour
Windows 64 will use the Windows 32 flavour

Note: this information is not used to select the toolchain during compilation. If you want a specific version to be used, you should use the notation {runtime.tools.TOOLNAME-VERSION.path} in the platform.txt.

Platforms definitions

Finally, let's see how PLATFORMS are made.

        {
          "name": "Arduino AVR Boards",
          "architecture": "avr",
          "version": "1.6.6",
          "category": "Arduino",
          "help": {
            "online": "http://www.arduino.cc/en/Reference/HomePage"
          },
          "url": "http://downloads.arduino.cc/cores/avr-1.6.6.tar.bz2",
          "archiveFileName": "avr-1.6.6.tar.bz2",
          "checksum": "SHA-256:08ad5db4978ebea22344edc5d77dce0923d8a644da7a14dc8072e883c76058d8",
          "size": "4876916",
          "boards": [
            {"name": "Arduino Yún"},
            {"name": "Arduino Uno"},
            {"name": "Arduino Diecimila"},
            {"name": "Arduino Nano"},
            {"name": "Arduino Mega"},
            {"name": "Arduino MegaADK"},
            {"name": "Arduino Leonardo"},
          ],
          "toolsDependencies": [
            { "packager": "arduino", "name": "avr-gcc", "version": "4.8.1-arduino5" },
            { "packager": "arduino", "name": "avrdude", "version": "6.0.1-arduino5" }
          ],
          "discoveryDependencies": [
            { "packager": "arduino", "name": "serial-discovery" },
            { "packager": "arduino", "name": "mdns-discovery" }
          ],
          "monitorDependencies": [
            { "packager": "arduino", "name": "serial-monitor" }
          ]
        },

Each PLATFORM describes a core for a specific architecture. The fields needed are:

name: the extended name of the platform that is displayed on the Boards Manager GUI
architecture: is the architecture of the platform (avr, sam, etc...). It must match the architecture of the core as explained in the Arduino platform specification
version: the version of the platform.
deprecated: (optional) setting to true causes the platform to be moved to the bottom of all Boards Manager and arduino-cli core listings and marked "DEPRECATED".
category: this field is reserved, a 3rd party core must set it to Contributed
help/online: is a URL that is displayed on the Arduino IDE's Boards Manager as an "Online Help" link
url, archiveFileName, size and checksum: metadata of the core archive file. The meaning is the same as for the TOOLS
boards: the list of boards supported (note: just the names to display on the Arduino IDE's Boards Manager GUI! the real boards definitions are inside boards.txt inside the core archive file)
toolsDependencies: the tools needed by this platform. They will be installed by Boards Manager along with the platform. Each tool is referenced by the triple (packager, name, version) as previously said. Note that you can reference tools available in other packages as well, even if no platform of that package is installed.
discoveryDependencies: the Pluggable Discoveries needed by this platform. These are tools, defined exactly like the ones referenced in toolsDependencies. Unlike toolsDependencies, discoveries are referenced by the pair (packager, name). The version is not specified because the latest installed discovery tool will always be used. Like toolsDependencies they will be installed by Boards Manager along with the platform and can reference tools available in other packages as well, even if no platform of that package is installed.
monitorDependencies: the Pluggable Monitors needed by this platform. These are tools, defined exactly like the ones referenced in toolsDependencies. Unlike toolsDependencies, monitors are referenced by the pair (packager, name). The version is not specified because the latest installed monitor tool will always be used. Like toolsDependencies they will be installed by Boards Manager along with the platform and can reference tools available in other packages as well, even if no platform of that package is installed.

The version field is validated by both Arduino IDE and JSemVer. Here are the rules Arduino IDE follows for parsing versions (source):

Split the version at the - character and continue with the first part.
If there are no dots (.), parse version as an integer and form a Version from that integer using Version.forIntegers
If there is one dot, split version into two, parse each part as an integer, and form a Version from those integers using Version.forIntegers
Otherwise, simply parse version into a Version using Version.valueOf

Note: if you miss a bracket in the JSON index, then add the URL to your Preferences, and open Boards Manager it can cause the Arduino IDE to no longer load until you have deleted the file from your arduino15 folder.

How a tool's path is determined in platform.txt

When the IDE needs a tool, it downloads the corresponding archive file and unpacks the content into a private folder that can be referenced from platform.txt using one of the following properties:

{runtime.tools.TOOLNAME-VERSION.path}
{runtime.tools.TOOLNAME.path}

For example, to obtain the avr-gcc 4.8.1 folder we can use {runtime.tools.avr-gcc-4.8.1.path} or {runtime.tools.avr-gcc.path}.

In general the same tool may be provided by different packagers (for example the Arduino packager may provide an arduino:avr-gcc and another 3rd party packager may provide their own 3rdparty:avr-gcc). The rules to disambiguate are as follows:

The property {runtime.tools.TOOLNAME.path} points, in order of priority, to:
1. the tool, version and packager specified via toolsDependencies in the package_index.json
2. the highest version of the tool provided by the packager of the current platform
3. the highest version of the tool provided by the packager of the referenced platform used for compile (see "Referencing another core, variant or tool" for more info)
4. the highest version of the tool provided by any other packager (in case of tie, the first packager in alphabetical order wins)
The property {runtime.tools.TOOLNAME-VERSION.path} points, in order of priority, to:
1. the tool and version provided by the packager of the current platform
2. the tool and version provided by the packager of the referenced platform used for compile (see "Referencing another core, variant or tool" for more info)
3. the tool and version provided by any other packager (in case of tie, the first packager in alphabetical order wins)

Example JSON index file

{
  "packages": [
    {
      "name": "myboard",
      "maintainer": "Jane Developer",
      "websiteURL": "https://github.com/janedeveloper/myboard",
      "email": "jane@janedeveloper.org",
      "help": {
        "online": "http://janedeveloper.org/forum/myboard"
      },
      "platforms": [
        {
          "name": "My Board",
          "architecture": "avr",
          "version": "1.0.0",
          "category": "Contributed",
          "help": {
            "online": "http://janedeveloper.org/forum/myboard"
          },
          "url": "https://janedeveloper.github.io/myboard/myboard-1.0.0.zip",
          "archiveFileName": "myboard-1.0.0.zip",
          "checksum": "SHA-256:ec3ff8a1dc96d3ba6f432b9b837a35fd4174a34b3d2927de1d51010e8b94f9f1",
          "size": "15005",
          "boards": [{ "name": "My Board" }, { "name": "My Board Pro" }],
          "toolsDependencies": [
            {
              "packager": "arduino",
              "name": "avr-gcc",
              "version": "4.8.1-arduino5"
            },
            {
              "packager": "arduino",
              "name": "avrdude",
              "version": "6.0.1-arduino5"
            }
          ]
        },
        {
          "name": "My Board",
          "architecture": "avr",
          "version": "1.0.1",
          "category": "Contributed",
          "help": {
            "online": "http://janedeveloper.org/forum/myboard"
          },
          "url": "https://janedeveloper.github.io/myboard/myboard-1.0.1.zip",
          "archiveFileName": "myboard-1.0.1.zip",
          "checksum": "SHA-256:9c86ee28a7ce9fe33e8b07ec643316131e0031b0d22e63bb398902a5fdadbca9",
          "size": "15125",
          "boards": [{ "name": "My Board" }, { "name": "My Board Pro" }],
          "toolsDependencies": [
            {
              "packager": "arduino",
              "name": "avr-gcc",
              "version": "4.8.1-arduino5"
            },
            {
              "packager": "arduino",
              "name": "avrdude",
              "version": "6.0.1-arduino5"
            }
          ]
        }
      ],
      "tools": []
    }
  ]
}

In the example there is one PACKAGE, My Board. The package is compatible with the AVR architecture. There are two versions of the PACKAGE, 1.0.0 and 1.0.1. No TOOLS needed to be installed so that section was left empty.

Here is the Boards Manager entry created by the example:

Archive structure

It must contain a single folder in the root. All files and __MACOSX folder present in the root will be ignored.

Valid structure

.
└── avr/
    ├── bootloaders
    ├── cores
    ├── firmwares
    ├── libraries
    ├── variants
    ├── boards.txt
    ├── platform.txt
    └── programmers.txt

Invalid structure:

.
├── avr/
│   ├── ...
│   ├── boards.txt
│   ├── platform.txt
│   └── programmers.txt
├── folder2
└── folder3

Note: the folder structure of the core archive is slightly different from the standard manually installed Arduino IDE 1.5+ compatible hardware folder structure. You must remove the architecture folder(e.g., avr or arm), moving all the files and folders within the architecture folder up a level.

Installation

The installation archives contain the Board support files.

Supported formats are .zip, .tar.bz2, and .tar.gz. Starting from Arduino CLI >=0.30.0 support for .tar.xz, and .tar.zst has been added, by the way, if you want to keep compatibility with older versions of Arduino IDE and Arduino CLI we recommend using one of the older formats.

The folder structure of the core archive is slightly different from the standard manually installed Arduino IDE 1.5+ compatible hardware folder structure. You must remove the architecture folder(e.g., avr or arm), moving all the files and folders within the architecture folder up a level.

After adding Boards Manager support for your boards, please share the JSON index file URL on the Unofficial list of 3rd party boards support urls.

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package_index_json-specification.md

package_index_json-specification.md

Naming of the JSON index file

JSON Index file contents

Tools definitions

Tools flavours (available builds made for different OS)

Platforms definitions

How a tool's path is determined in platform.txt

Example JSON index file

Archive structure

Installation

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package_index_json-specification.md

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package_index_json-specification.md

File metadata and controls

Naming of the JSON index file

JSON Index file contents

Tools definitions

Tools flavours (available builds made for different OS)

Platforms definitions

How a tool's path is determined in platform.txt

Example JSON index file

Archive structure

Installation