Erlang/OTP 29 is a new major release with new features, improvements as well as a few incompatibilities. Some of the new features are highlighted below.

Many thanks to all contributors!

Highlights #

• Added support for -unsafe attributes for marking functions as unsafe to use. The compiler will by default now generate warnings for calls to functions in Erlang/OTP known to be always unsafe. Furthermore, xref can now be used to find calls to unsafe functions and functions that lack documentation.

• The SSH daemon now defaults to disabled for shell and exec services, implementing the “secure by default” principle. This prevents authenticated users from executing arbitrary Erlang code unless explicitly configured.

• The SFTP subsystem is no longer enabled by default when starting an SSH daemon.

• In SSL, the post quantum hybrid algorithm x25519mlkem768 is now the most preferred key exchange group in the default configuration.

• The module io_ansi allows the user to emit Virtual Terminal Sequences (also known as ANSI sequences) to the terminal in order to add colors/styling to text or to create fully fledged terminal applications.

• The new ct_doctest module allows the user to test documentation examples in Erlang module docs and documentation files.

• The ignore_xref attribute has been handled as a post-analysis filter by build tools such as Rebar3. In this release, [xref] itself does the filtering, ensuring that all tooling that calls xref for any purpose can rely on these declarations to just work.

General #

• In the default code path for the Erlang system, the current working directory (.) is now in the last position instead of the first.

• There is no longer a 32-bit Erlang/OTP build for Windows.

New language features #

• Native records as described in EEP-79 has been implemented. A native record is a data structure similar to the traditional tuple-based records, except that is a true data type. Native records are considered experimental in Erlang/OTP 29 and possibly also in Erlang/OTP 30.

• The new is_integer/3 guard BIF makes it possible to easily verify that a value is both an integer and within a certain range. For example: is_integer(I, 0, 100)

• Multi-valued comprehensions according to EEP 78 are now supported. For example, [-I, I || I <- [1, 2, 3]] will produce [-1,1,-2,2,-3,3].

• By enabling the compr_assign feature, it is now possible to bind variables in a comprehensions. For example: [H || E <- List, H = erlang:phash2(E), H rem 10 =:= 0]

Compiler and JIT improvements #

• In the documentation for the [compile] module, there is now a section with recommendations for implementors of languages running on the BEAM.

• The JIT now generates better code for matching or creating binaries with multiple little-endian segments.

• The compiler will generate more efficient code for map comprehensions with constant values that don’t depend on the generator. Example: #{K => 42 || K <- List}

Compiler warnings #

There are several new compiler warnings enabled by default. For each such warning, there is an option to disable it.

• There will now be a warning when using the catch operator, which has been deprecated for a long time. It is recommended to instead use try…catch but is also possible to disable the warning by using the nowarn_deprecated_catch option.

• There will now be a warning when exporting variables out of a subexpression. For example: file:open(File, AllOpts = [write, {encoding,utf8}]). This warning can be disabled using the nowarn_export_var_subexpr compiler option.

• The compiler will now warn for uses of the and and or operators. This warning can be disabled using the nowarn_obsolete_bool_op compiler option.

• The compiler will now warn for matches such as {a,B} = {X,Y}, which is better written as {a=X,B=Y}. This warning can be disabled using the nowarn_match_alias_pats option.

For a long time, there has been a warning for using the obsolete guard tests (such as list(L) instead of is_list(L). In Erlang/OTP 30, the old guards will be removed from the language.

STDLIB #

• There are new functions for randomly permutating a list: rand:shuffle/1 and rand:shuffle_s/2.

SSH #

• The default key exchange algorithm is now mlkem768x25519-sha256, a hybrid quantum-resistant algorithm combining ML-KEM-768 with X25519. This provides protection against both classical and quantum computer attacks while maintaining backward compatibility through automatic fallback to other algorithms when peers don’t support it.

For a full list and more details about new features and potential incompatibilities see the README.