Compatibility and Deprecations

Compatibility between Elixir and Erlang/OTP

Erlang/OTP versioning is independent from the versioning of Elixir. Each version of Elixir supports a specific range of Erlang/OTP versions. The compatibility table is shown below.

Elixir version	Supported Erlang/OTP versions
1.0	17 - 17 (and OTP 18 from v1.0.5)
1.1	17 - 18
1.2	18 - 18 (and OTP 19 from v1.2.6)
1.3	18 - 19
1.4	18 - 19 (and OTP 20 from v1.4.5)
1.5	18 - 20
1.6	19 - 20

While Elixir often adds compatibility to new Erlang versions on released branches, such as support for OTP 20 in v1.4.5, those releases usually contain the minimum changes for Elixir to run without errors. Only the next minor release, in this case v1.5.0, does effectively leverage the new features provided by the latest Erlang release.

Deprecations

Policy

Elixir deprecations happen in 3 steps:

1. The feature is soft-deprecated. It means both CHANGELOG and documentation must list the feature as deprecated but no warning is effectively emitted by running the code. There is no requirement to soft-deprecate a feature.

2. The feature is effectively deprecated by emitting warnings on usage. In order to deprecate a feature, the proposed alternative MUST exist for AT LEAST two versions. For example, Enum.uniq/2 was soft-deprecated in favor of Enum.uniq_by/2 in Elixir v1.1. This means a deprecation warning may only be emitted by Elixir v1.3 or later.

3. The feature is removed. This can only happen on major releases. This means deprecated features in Elixir v1.x shall only be removed by Elixir v2.x.

Table of deprecations

Deprecated feature	Deprecated in	Replaced by (available since)
Enum.partition/2	v1.6	Enum.split_with/2 (v1.4)
Keyword.replace/3	v1.6	Use Keyword.fetch/2 + Keyword.put/3 (v1.0)
Macro.unescape_tokens/1 and Macro.unescape_tokens/2	v1.6	Use Enum.map/2 to traverse over the arguments (v1.0)
Map.replace/3	v1.6	Use Map.fetch/2 + Map.put/3 (v1.0)
Range.range?/1	v1.6	Pattern match on _.._ instead (v1.0)
Atom.to_char_list/1	v1.5	Atom.to_charlist/1 (v1.3)
Enum.filter_map/3	v1.5	Enum.filter/2 + Enum.map/2 or for comprehensions (v1.0)
Float.to_char_list/1	v1.5	Float.to_charlist/1 (v1.3)
GenEvent module	v1.5	Supervisor and GenServer (v1.0); GenStage (v1.3); :gen_event (OTP 17)
Integer.to_char_list/1 and Integer.to_char_list/2	v1.5	Integer.to_charlist/1 and Integer.to_charlist/2 (v1.3)
Kernel.to_char_list/1	v1.5	Kernel.to_charlist/1 (v1.3)
List.Chars.to_char_list/1	v1.5	List.Chars.to_charlist/1 (v1.3)
Stream.filter_map/3	v1.5	Stream.filter/2 + Stream.map/2 (v1.0)
String.ljust/3 and String.rjust/3	v1.5	String.pad_leading/3 and String.pad_trailing/3 with a binary padding (v1.3)
String.strip/1 and String.strip/2	v1.5	String.trim/1 and String.trim/2 (v1.3)
String.lstrip/1 and String.rstrip/1	v1.5	String.trim_leading/1 and String.trim_trailing/1 (v1.3)
String.lstrip/2 and String.rstrip/2	v1.5	String.trim_leading/2 and String.trim_trailing/2 with a binary as second argument (v1.3)
String.to_char_list/1	v1.5	String.to_charlist/1 (v1.3)
() to mean nil	v1.5	nil (v1.0)
:as_char_lists value in Inspect.Opts.t/0 type	v1.5	:as_charlists (v1.3)
:char_lists key in Inspect.Opts.t/0 type	v1.5	:charlists (v1.3)
char_list/0 type	v1.5	charlist/0 type (v1.3)
@compile {:parse_transform, _} in Module	v1.5	None
EEx: <%= in middle and end expressions	v1.5	Use <% (= is allowed only on start expressions) (v1.0)
Access.key/1	v1.4	Access.key/2 (v1.3)
Behaviour module	v1.4	@callback (v1.0)
Enum.uniq/2	v1.4	Enum.uniq_by/2 (v1.2)
Float.to_char_list/2	v1.4	:erlang.float_to_list/2 (OTP 17)
Float.to_string/2	v1.4	:erlang.float_to_binary/2 (OTP 17)
HashDict module	v1.4	Map (v1.2)
HashSet module	v1.4	MapSet (v1.1)
Set module	v1.4	MapSet (v1.1)
Stream.uniq/2	v1.4	Stream.uniq_by/2 (v1.2)
IEx.Helpers.import_file/2	v1.4	IEx.Helpers.import_file_if_available/1 (v1.3)
Mix.Utils.camelize/1	v1.4	Macro.camelize/1 (v1.2)
Mix.Utils.underscore/1	v1.4	Macro.underscore/1 (v1.2)
Variable used as function call	v1.4	Use parentheses (v1.0)
Anonymous functions with no expression after ->	v1.4	Use an expression or explicitly return nil (v1.0)
Dict module	v1.3	Keyword (v1.0) or Map (v1.2)
Keyword.size/1	v1.3	Kernel.length/1 (v1.0)
Map.size/1	v1.3	Kernel.map_size/1 (v1.0)
Set behaviour	v1.3	MapSet data structure (v1.1)
String.valid_character?/1	v1.3	String.valid?/1 (v1.0)
Task.find/2	v1.3	Use direct message matching (v1.0)
:append_first option in Kernel.defdelegate/2	v1.3	Define the function explicitly (v1.0)
/r option in Regex	v1.3	/U (v1.1)
\x{X*} inside strings/sigils/charlists	v1.3	\uXXXX or \u{X*} (v1.1)
Map or dictionary as second argument in Enum.group_by/3	v1.3	Use Enum.reduce/3 (v1.0)
Non-map as second argument in URI.decode_query/2	v1.3	Use a map (v1.0)
Dict behaviour	v1.2	MapSet data structure (v1.1)
Access protocol	v1.1	Access behaviour (v1.1)
as: true | false in alias/2 and require/2	v1.1	None
?\xHEX	v1.1	0xHEX (v1.0)