Emscripten SDK (emsdk)

** Emscripten SDK (** emsdk ) is used to perform all SDK maintenance. You only need to install the SDK once; after that emsdk can do all further updates!

With emsdk you can download, install or remove any SDK or Tool, and even use the bleeding edge versions in development on Github. To access the emsdk on Windows, first launch the Emscripten Command Prompt. Most operations are of the form ./emsdk command.

This document provides the command syntax, and a set of guides explaining how to perform both common and advanced maintenance operations.

Command line syntax

./emsdk [help [–old] | list | update | install <tool/sdk> | uninstall <tool/sdk> | activate <tool/sdk>]


Command Description
list [--old] Lists all current SDKs and tools and their installation status. With the --old parameter, historical versions are also shown.
update Fetches the latest list of all available tools and SDKs (but does not install them).
install <tool/sdk> Downloads and installs the specified tool or SDK.
uninstall <tool/sdk> Removes the specified tool or SDK from the disk.
activate <tool/sdk> Sets the specified tool or SDK as the default tool in the system environment. On Linux you additionally have to enable the environment settings using source ./emsdk_env.sh, as described in “How do I change the currently active SDK version?”.
help Lists all supported commands. The same list is output if no command is specified.


  • For Linux and Mac OSX the commands are called with ./emsdk. On Windows use emsdk.

Tools and SDK targets

The <tool/sdk> given above as a command argument is one of the targets listed using ./emsdk list (or ./emsdk list --old).

Note that some of the tools and SDK names include master or incoming: these targets are used to clone and pull the very latest versions from the Emscripten incoming and master branches.

You can also specify a target of latest to grab the most current SDK.

SDK concepts

The Emscripten toolchain includes a number of different tools, including Clang, Emscripten, Java, Git, Node, etc. Emsdk is a small package manager for controlling which tools are installed, and from the set of installed tools, which are active.

The current set of available tools and SDKs are listed using ./emsdk list. These can be installed individually (./emsdk install node-0.10.17-64bit) or as a group (./emsdk install node-0.10.17-64bit java-7.45-64bit).

The SDK targets are a convenience mechanism for specifying the full set of tools used by a particular Emscripten release. For example, the two lines below are equivalent:

./emsdk install sdk-incoming-64bit
./emsdk install git-1.8.3 clang-incoming-64bit node-0.10.17-64bit python- java-7.45-64bit emscripten-incoming

A particular installed SDK (or tool) can then be set as active, meaning that it will be used when Emscripten is run. The active “compiler configuration” is stored in a user-specific file (~/.emscripten), which is discussed in the next section.


The different tools and SDKs managed by emsdk are stored in different directories under the root folder you specified when you first installed an SDK, grouped by tool and version.

Emscripten Compiler Configuration File (.emscripten)

The Compiler Configuration File stores the active configuration on behalf of the emsdk. The active configuration defines the specific set of tools that are used by default if Emscripten in called on the Emscripten Command Prompt.

The configuration file is named .emscripten. It is user-specific, and is located in the user’s home directory (~/.emscripten on Linux).

The file should generally not be updated directly unless you’re building Emscripten from source. Instead use the emsdk to activate specific SDKs and tools as needed (emsdk activate <tool/SDK>).

Below are typical .emscripten files created by emsdk. Note the variable names used to point to the different tools:

# .emscripten file from Windows SDK

import os
NODE_JS = 'node'
LLVM_ROOT='C:/Program Files/Emscripten/clang/e1.21.0_64bit'
NODE_JS='C:/Program Files/Emscripten/node/0.10.17_64bit/node.exe'
PYTHON='C:/Program Files/Emscripten/python/'
EMSCRIPTEN_ROOT='C:/Program Files/Emscripten/emscripten/1.21.0'
JAVA='C:/Program Files/Emscripten/java/7.45_64bit/bin/java.exe'
V8_ENGINE = ''
TEMP_DIR = 'c:/users/hamis_~1/appdata/local/temp'
# .emscripten file from Linux SDK

import os
NODE_JS = 'nodejs'
V8_ENGINE = ''
TEMP_DIR = '/tmp'

“How to” guides

The following topics explain how to perform both common and advanced maintenance operations, ranging from installing the latest SDK through to installing your own fork from Github.


The examples below show the commands for Linux and Mac OS X. The commands are the same on Windows, but you need to replace ./emsdk with emsdk.

How do I just get the latest SDK?

Use the update argument to fetch the current registry of available tools, and then specify the latest install target to get the most recent SDK:

# Fetch the latest registry of available tools.
./emsdk update

# Download and install the latest SDK tools.
./emsdk install latest

# Set up the compiler configuration to point to the "latest" SDK.
./emsdk activate latest

How do I use emsdk?

Use ./emsdk help or just ./emsdk to get information about all available commands.

How do I check which versions of the SDK and tools are installed?

To get a list of all currently installed tools and SDK versions (and all available tools) run:

./emsdk list

A line will be printed for each tool and SDK that is available for installation. The text INSTALLED will be shown for each tool that has already been installed. If a tool/SDK is currently active, a star (*) will be shown next to it.

How do I install a tool/SDK version?

Use the install argument to download and install a new tool or SDK version:

./emsdk install <tool/sdk name>


An installed tool is present on the local machine, but not necessarily the active environment. To make an installed SDK active, use the activate command.

How do I remove a tool or an SDK?

Use the uninstall argument to delete a given tool or SDK from the local computer:

./emsdk uninstall <tool/sdk name>

If you want to completely remove Emscripten from your system, follow the guide at Uninstalling the Emscripten SDK.

How do I check for updates to the Emscripten SDK?

First use the update command to fetch package information for all new tools and SDK versions. Then use install <tool/sdk name> to install a new version:

# Fetch the latest registry of available tools.
./emsdk update

# Download and install the specified new version.
./emsdk install <tool/sdk name>

How do I change the currently active SDK version?

Toggle between different tools and SDK versions using the activate command. This will set up ~/.emscripten to point to that particular tool:

./emsdk activate <tool/sdk name>

# On Linux and OSX, also set the environment variables.
source ./emsdk_env.sh


On Linux and Mac OS X, activate writes the required information to the configuration file, but cannot automatically set up the environment variables in the current terminal. To do this you need to call source ./emsdk_env.sh after calling activate. The use of source is a security feature of Unix shells.

On Windows, calling activate automatically sets up the required paths and environment variables.

How do I install and activate old Emscripten SDKs and tools?

Emsdk contains a history of old tools and SDKs that you can use to maintain your migration path. Use the list --old argument to get a list of archived tool and SDK versions, and install <name_of_tool> to install a specific tool:

# Get list of the old versions of the tool.
./emsdk list --old

# Install the required version.
./emsdk install <name_of_tool>

# Activate required version.
./emsdk activate <name_of_tool>

On Windows, you can directly install an old SDK version by using one of these archived NSIS installers.

How do I track the latest Emscripten development with the SDK?

It is also possible to use the latest and greatest versions of the tools on the Github repositories! This allows you to obtain new features and latest fixes immediately as they are pushed to Github, without having to wait for release to be tagged. No Github account or fork of Emscripten is required.

To switch to using the latest upstream git development branch (incoming), run the following:

# Install git. Skip if the system already has it.
./emsdk install git-1.8.3

# Clone+pull the latest kripken/emscripten/incoming.
./emsdk install sdk-incoming-64bit

# Set the "incoming SDK" as the active version.
./emsdk activate sdk-incoming-64bit

If you want to use the upstream stable branch master, then replace -incoming- with -master- in the commands above.

How do I use my own Emscripten Github fork with the SDK?

It is also possible to use your own fork of the Emscripten repository via the SDK. This is useful in the case when you want to make your own modifications to the Emscripten toolchain, but still keep using the SDK environment and tools.

The way this works is that you first install the sdk-incoming SDK as in the previous section. Then you use familiar git commands to replace this branch with the information from your own fork:

cd emscripten/incoming

# Add a git remote link to your own repository.
git remote add myremote https://github.com/mygituseraccount/emscripten.git

# Obtain the changes in your link.
git fetch myremote

# Switch the emscripten-incoming tool to use your fork.
git checkout -b myincoming --track myremote/incoming

You can switch back and forth between remotes via the git checkout command as usual.