Erlang/OTP 18.0-rc1 is available for testing.


This is an alpha release, which will be followed by a planned beta release in May and a final OTP 18.0 product release in June 2015.

Between the alpha and beta and final release there will be new updates of the master branch with corrections and minor new features. Occasionally there might be new tags which we in that case will communicate and ask you to test.

Erlang/OTP 18.0 is a new major release with new features, quite a few (characteristics) improvements, as well as a few incompatibilities. 

See the Release Notes and the documentation for more details.

We would like to ask you to build and test the alpha release and send us your feedback as soon as possible, so that we can make the necessary corrections before OTP 18.0-rc2 and OTP 18.0, respectively.

The release contains many changes; thus, some unexpected incompatibilities or issues may have slipped through our tests. Please try to build and run your current products/applications and let us know about any problems.

IMPORTANT INFO when building your own code with this OTP release

Since erlang:now is deprecated your build might stop if you are using "warnings as errors".

To let the build through you can turn of warnings for deprecated functions by setting an environment variable like this:

export ERL_COMPILER_OPTIONS=nowarn_deprecated_function

Some highlights of the release are:

  • dialyzer: The -dialyzer() attribute can be used for suppressing warnings in a module by specifying functions or warning options. It can also be used for requesting warnings in a module.
  • erts: The time functionality has been extended. This includes a new API for time, as well as "time warp" modes which alters the behavior when system time changes. You are strongly encouraged to use the new API instead of the old API based on erlang:now/0. erlang:now/0 has been deprecated since it will always be a scalability bottleneck. For more information see the Time and Time Correction chapter of the ERTS User's Guide. Here is a link
  • erts: Beside the API changes and time warp modes a lot of scalability and performance improvements regarding time management has been made. Examples are:
    • scheduler specific timer wheels,
    • scheduler specific BIF timer management,
    • parallel retrieval of monotonic time and system time on OS:es that support it.
  • erts: The previously introduced "eager check I/O" feature is now enabled by default.
  • erts/compiler: enhanced support for maps. Big maps new uses a HAMT (Hash Array Mapped Trie) representation internally which makes them more efficient. There is now also support for variables as map keys.  
  • ssl: Remove default support for SSL-3.0 and added padding check for TLS-1.0 due to the Poodle vulnerability.
  • ssl: Remove default support for RC4 cipher suites, as they are consider too weak.
  • stdlib: Allow maps for supervisor flags and child specs


You can find the Release Notes with more detailed info at

You find the source code at in the official Erlang repository.

Git tag OTP-18.0-rc1

You can also read the documentation on-line here: (see the Release Notes mentioned above for release notes which are not updated in the doc, but the new functionality is)

We also want to thank those that sent us patches, suggestions and bug reports.

The Erlang/OTP Team at Ericsson