Erlang/OTP 21.0 is a new major release with new features, quite a few improvements, as well as some potential incompatibilities.

OTP 21.0 Readme File

OTP 21.0 Source File (89454983)

OTP 21.0.1 Windows 32-bit Binary File (89454983)

OTP 21.0.1 Windows 64-bit Binary File (91707927)

OTP 21.0 HTML Documentation File (32501093)

OTP 21.0 Man Pages File (1311959)

Due to a bug in the emulator on windows systems regarding os:getenv we have updated the windows installers with the fix.

This new version is 21.0.1 and the full release notes for that can be found HERE

OTP 21

Erlang/OTP 21 is a new major release with new features, improvements as well as incompatibilities.

Potential Incompatibilities

  • All Corba applications are now moved from the OTP repository
  • A new Corba repository will be created
  • New applications ftp and tftp, moved from inets
  • ssl no longer supports 3_DES cipher suites or RSA-key exchange cipher suites by default
  • erlang:monitor on a primitive node (erl_interface, jinterface, etc) will no longer fail with badarg exception. Instead a monitor will be created, but it will only supervise the connection to the node.



  • Enhanced IO scalability
  • Support for usage of distribution controller processes for alternative transports, routing etc
  • compact instructions on 64bit systems for code below 4GB 20% less memory for loaded code
  • Rewrite of the efile-driver with NIFs and "Dirty schedulers" resulting in faster file operations
  • non-smp VM removed
  • link and monitor optimized for scalability
  • os:getenv/putenv now work on thread-safe emulation. No longer in sync with libc getenv(3). Manual synchronization will be needed.


  • Misc compiler optimizations including contributions from the Elixir team resulting in 10% improvements in benchmarks
  • "Tuple calls" have been removed from the run-time system.
  • Code such as f({ok, Val}) -> {ok, Val} is now automatically rewritten to f({ok, Val} = Tuple) -> Tuple. this reduces code size, execution time, and removed GC pressure.
  • More information in stacktrace from a number of operators
  • erlang:get_stacktrace/0 deprecated to be replaced with try ... catch C:R:Stacktrace -> ...
  • Creation of small maps with literal keys optimized.
  • A new predifined macro `OTP_RELEASE` and preprocessor directives `-if` and `-elif`


  • DTLS is now supported in the SSL application
  • Enhanced support for distribution over TLS
  • "unsecure" ciphers removed from defaults in SSL and SSH.
  • A new option value defined to facilitate implementing exec servers. Old option kept for compatibility, but now gives errors on stderror.

Standard libraries:

  • New API for logging, logger
  • New uri_string module for parsing URIs according to "The standard"
  • New function lists:search(list,fun/1) -> {ok, Value} | false
  • Changed default behaviour of .erlang loading. escript, erlc, dialyzer and typer no longer load an .erlang at all.

For more details see

For installation instructions please consult the README file that is part of the distribution.

Online documentation can be browsed here:

The Erlang/OTP source can also be found at GitHub in the official Erlang repository, Here: OTP-21.0

Please report any new issues via Erlang/OTPs puplic issue tracker


We want to thank all of you who sent us patches, suggestions and bug reports!

Thank you for all your contributions!

The Erlang/OTP team at Ericsson

Compiling Erlang from source

You can build Erlang from source on your own, following the building and installation instructions. Or use the Kerl script. Kerl is a script that lets you easily build Erlang with a few commands. Follow the instructions to build.

Finding a source version

Follow this link that presents all released source versions, a link to the GitHub source tag, and to the README.

Pre-built Binary Packages

Most OS package managers provide pre-built binary packages. You can also download the latest stable releases from Erlang Solutions. Erlang Solutions provides pre-built binary packages for OS X, Windows, Ubuntu, Debian, Fedora, CentOS, Raspbian and other operating systems. 

  • For Homebrew on OS X: brew install erlang
  • For MacPorts on OS X: port install erlang
  • For Ubuntu and Debianapt-get install erlang
  • For Fedorayum install erlang
  • For FreeBSDpkg install erlang


Since OTP 18.0, Erlang/OTP is released under Apache License 2.0. The older releases prior to 18.0 were released under Erlang Public License (EPL), a derivative work of the Mozilla Public License (MPL).