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This repository began as a GitHub fork of joyent/node.

io.js contributions, releases, and contributorship are under an open governance model. We intend to land, with increasing regularity, releases which are compatible with the npm ecosystem that has been built to date for Node.js.

Is it io.js or IO.js or iojs or IOjs or iOjS?

The official name is io.js, which should never be capitalized, especially not at the start of a sentence, unless it is being displayed in a location that is customarily all-caps (such as the title of man pages).


Binaries, installers, and source tarballs are available at

Releases are available at, listed under their version string. The symlink will point to the latest release directory.

Nightly builds are available at, listed under their version string which includes their date (in UTC time) and the commit SHA at the HEAD of the release.

API documentation is available in each release and nightly directory under docs. points to the latest version.

Verifying Binaries

Release and nightly download directories all contain a SHASUM256.txt file that lists the SHA checksums for each file available for download. To check that a downloaded file matches the checksum, run it through sha256sum with a command such as:

$ grep iojs-vx.y.z.tar.gz SHASUMS256.txt | sha256sum -c -

(Where "iojs-vx.y.z.tar.gz" is the name of the file you have downloaded)

Additionally, releases (not nightlies) have GPG signed copies of SHASUM256.txt files available as SHASUM256.txt.asc. You can use gpg to verify that the file has not been tampered with.

To verify a SHASUM256.txt.asc, you will first need to import all of the GPG keys of individuals authorized to create releases. They are listed at the bottom of this README. Use a command such as this to import the keys:

$ gpg --keyserver \
  --recv-keys DD8F2338BAE7501E3DD5AC78C273792F7D83545D

(Include each of the key fingerprints at the end of this command.)

You can then use gpg --verify SHASUMS256.txt.asc to verify that the file has been signed by an authorized member of the io.js team.

Once verified, use the SHASUMS256.txt.asc file to get the checksum for the binary verification command above.


Unix / Macintosh


  • gcc and g++ 4.8 or newer, or
  • clang and clang++ 3.4 or newer
  • Python 2.6 or 2.7
  • GNU Make 3.81 or newer
  • libexecinfo (FreeBSD and OpenBSD only)
$ ./configure
$ make
$ [sudo] make install

If your Python binary is in a non-standard location or has a non-standard name, run the following instead:

$ export PYTHON=/path/to/python
$ $PYTHON ./configure
$ make
$ [sudo] make install

To run the tests:

$ make test

To build the documentation:

$ make doc

To read the documentation:

$ man doc/iojs.1



  • Python 2.6 or 2.7
  • Visual Studio 2013 for Windows Desktop, or
  • Visual Studio Express 2013 for Windows Desktop
  • Basic Unix tools required for some tests, Git for Windows includes Git Bash and tools which can be included in the global PATH.
> vcbuild nosign

To run the tests:

> vcbuild test

Android / Android based devices, aka. Firefox OS

Be sure you have downloaded and extracted [Android NDK] ( before in a folder. Then run:

$ ./android-configure /path/to/your/android-ndk
$ make

Intl (ECMA-402) support:

Intl support is not enabled by default.

"small" (English only) support

This option will build with "small" (English only) support, but the full Intl (ECMA-402) APIs. With --download=all it will download the ICU library as needed.

Unix / Macintosh:

$ ./configure --with-intl=small-icu --download=all


> vcbuild small-icu download-all

The small-icu mode builds with English-only data. You can add full data at runtime.

Note: more docs are on the joyent/node wiki.

Build with full ICU support (all locales supported by ICU):

With the --download=all, this may download ICU if you don't have an ICU in deps/icu.

Unix / Macintosh:

$ ./configure --with-intl=full-icu --download=all


> vcbuild full-icu download-all

Build with no Intl support :-(

The Intl object will not be available. This is the default at present, so this option is not normally needed.

Unix / Macintosh:

$ ./configure --with-intl=none


> vcbuild intl-none

Use existing installed ICU (Unix / Macintosh only):

$ pkg-config --modversion icu-i18n && ./configure --with-intl=system-icu

Build with a specific ICU:

You can find other ICU releases at the ICU homepage. Download the file named something like icu4c-**##.#**-src.tgz (or .zip).

Unix / Macintosh

# from an already-unpacked ICU:
$ ./configure --with-intl=[small-icu,full-icu] --with-icu-source=/path/to/icu

# from a local ICU tarball
$ ./configure --with-intl=[small-icu,full-icu] --with-icu-source=/path/to/icu.tgz

# from a tarball URL
$ ./configure --with-intl=full-icu --with-icu-source=http://url/to/icu.tgz


First unpack latest ICU to deps/icu icu4c-##.#-src.tgz (or .zip) as deps/icu (You'll have: deps/icu/source/...)

> vcbuild full-icu

Resources for Newcomers

Current Project Team Members

The io.js project team comprises a group of core collaborators and a sub-group that forms the Technical Committee (TC) which governs the project. For more information about the governance of the io.js project, see

Collaborators follow the in maintaining the io.js project.