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Duktape - embeddable Javascript engine with a focus on portability and compact footprint
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Update CBOR absent tag document, add assigned tag number 31
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config Change header used for byteorder detection for modern Solaris Sep 21, 2019
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misc Manual perf test for app literal usage Nov 19, 2017
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references Add 'make refs' target to download ES specs Mar 8, 2016
runtests Use 'ECMAScript' spelling in misc places Apr 28, 2018
src-input Allow function declarations in strict mode Dec 9, 2019
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AUTHORS.rst Change header used for byteorder detection for modern Solaris Sep 21, 2019 Fix minor typos May 31, 2018
LICENSE.txt Preparations for 2.4.0 release Jul 28, 2019
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RELEASES.rst Releases: function statement in strict mode Dec 9, 2019
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Build Status


Duktape is an embeddable Javascript engine, with a focus on portability and compact footprint.

Duktape is easy to integrate into a C/C++ project: add duktape.c, duktape.h, and duk_config.h to your build, and use the Duktape API to call ECMAScript functions from C code and vice versa.

Main features:

  • Embeddable, portable, compact
  • ECMAScript E5/E5.1 compliant, with some semantics updated from ES2015+
  • Partial support for ECMAScript 2015 (E6) and ECMAScript 2016 (E7), Post-ES5 feature status, kangax/compat-table
  • ES2015 TypedArray and Node.js Buffer bindings
  • WHATWG Encoding API living standard
  • Built-in debugger
  • Built-in regular expression engine
  • Built-in Unicode support
  • Minimal platform dependencies
  • Combined reference counting and mark-and-sweep garbage collection with finalization
  • Custom features like coroutines
  • Property virtualization using a subset of ECMAScript ES2015 Proxy object
  • Bytecode dump/load for caching compiled functions
  • Distributable includes an optional logging framework, CommonJS-based module loading implementations, CBOR bindings, etc
  • Liberal MIT license (see LICENSE.txt)

See for packaged end-user downloads and documentation. The end user downloads are also available from the duktape-releases repo as both binaries and in unpacked form as git tags.

Have fun!


About this repository

This repository is intended for Duktape developers only, and contains Duktape internals: test cases, internal documentation, sources for the web site, etc.

Getting started: end user

When embedding Duktape in your application you should use the packaged source distributables available from See for the basics.

The distributable src/ directory contains a duk_config.h configuration header and amalgamated sources for Duktape default configuration. If necessary, use python tools/ to create header and sources for customized configuration options, see For example, to enable fastint support (example for Linux):

$ tar xvfJ duktape-2.0.0.tar.xz
$ cd duktape-2.0.0
$ rm -rf src-custom
$ python tools/ \
      --source-directory src-input \
      --output-directory src-custom \
      --config-metadata config \

# src-custom/ will now contain: duktape.c, duktape.h, duk_config.h.

You can also clone this repository, make modifications, and build a source distributable on Linux, macOS, and Windows using python util/ You'll need Python 2 and Python YAML binding.

Getting started: modifying and rebuilding the distributable

If you intend to change Duktape internals and want to rebuild the source distributable in Linux, macOS, or Windows:

# Linux; can often install from packages or using 'pip'
$ sudo apt-get install python python-yaml
$ python util/

# macOS
# Install Python 2.7.x
$ pip install PyYAML
$ python util/

# Windows
; Install Python 2.7.x from, and add it to PATH
> pip install PyYAML
> python util\

The source distributable directory will be in dist/.

For platform specific notes see

Getting started: other development (Linux only)

Other development stuff, such as building the website and running test cases, is based on a Makefile intended for Linux only. See detailed instructions in

There are some Docker images which can simplify the development setup. These are also intended for Linux only. For example:

# Build Docker images.  This takes a long time.
$ make docker-images

# Equivalent of 'make dist', but runs inside a container.
$ make docker-dist-src-wd

# Run a shell with /work/duktape containing a disposable master snapshot.
$ make docker-shell-master

# Run a shell with /work/duktape mounted from current directory.
# This allows editing, building, testing, etc with an interactive
# shell running in the container.
$ make docker-shell-wdmount

# For non-native images you may need:

Branch policy

  • The master branch is used for active development. While pull requests are tested before merging, master may be broken from time to time. When development on a new major release starts, master will also get API incompatible changes without warning. For these reasons you should generally not depend on the master branch for building your project; use a release tag or a release maintenance branch instead.

  • Pull requests and their related branches are frequently rebased so you should not fork off them. Pull requests may be open for a while for testing and discussion.

  • Release tags like v1.4.1 are used for releases and match the released distributables. These are stable once the release is complete.

  • Maintenance branches are used for backporting fixes and features for maintenance releases. Documentation changes go to master for maintenance releases too. For example, v1.5-maintenance was created for the 1.5.0 release and is used for 1.5.x maintenance releases.

  • A maintenance branch is also created for a major release when master moves on to active development of the next major release. For example, v1-maintenance was created when 1.5.0 was released (last planned 1.x release) and development of 2.0.0 (with API incompatible changes) started on master. The 1.6.0 and 1.7.0 releases were made from v1-maintenance for example.


Duktape uses Semantic Versioning for official releases. Builds from Duktape repo are not official releases and don't follow strict semver, mainly because DUK_VERSION needs to have some compromise value that won't be strictly semver conforming. Because Duktape tracks the latest ECMAScript specification versions, compliance fixes are made in minor versions even when they are technically not backwards compatible. See Versioning for details.

Reporting bugs


Security critical GitHub issues (for example anything leading to a segfault) are tagged security.



Copyright and license

See AUTHORS.rst and LICENSE.txt.

Duktape Wiki is part of Duktape documentation and under the same copyright and license.

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