# `mix deps.compile`
[🔗](https://github.com/elixir-lang/elixir/blob/7ff272706afc522e74121493b7166719985cb099/lib/mix/lib/mix/tasks/deps.compile.ex#L5)

Compiles dependencies.

By default, this task attempts to compile all dependencies.
A list of dependencies can be given to compile multiple
dependencies in order.

This task attempts to detect if the project contains one of
the following files and act accordingly:

  * `mix.exs` - invokes `mix compile`
  * `rebar.config` - invokes `rebar compile`
  * `Makefile.win`- invokes `nmake /F Makefile.win` (only on Windows)
  * `Makefile` - invokes `gmake` on DragonFlyBSD, FreeBSD, NetBSD, and OpenBSD,
    invokes `make` on any other operating system (except on Windows)

The compilation can be customized by passing a `compile` option
in the dependency:

    {:some_dependency, "0.1.0", compile: "command to compile"}

If a list of dependencies is given, Mix will attempt to compile
them as is. For example, if project `a` depends on `b`, calling
`mix deps.compile a` will compile `a` even if `b` is out of
date. This is to allow parts of the dependency tree to be
recompiled without propagating those changes upstream. To ensure
`b` is included in the compilation step, pass `--include-children`.

## Compiling dependencies across multiple OS processes

If you set the environment variable `MIX_OS_DEPS_COMPILE_PARTITION_COUNT`
to a number greater than 1, Mix will start multiple operating system
processes to compile your dependencies concurrently.

While Mix and Rebar compile all files within a given project in parallel,
enabling this environment variable can still yield useful gains in several
cases, such as when compiling dependencies with native code, dependencies
that must download assets, or dependencies where the compilation time is not
evenly distributed (for example, one file takes much longer to compile than
all others).

While most configuration in Mix is done via command line flags, this particular
environment variable exists because the best number will vary per machine
(and often per project too). The environment variable also makes it more accessible
to enable concurrent compilation in CI and also during `Mix.install/2` commands.

## Command line options

  * `--force` - force compilation of deps
  * `--skip-umbrella-children` - skips umbrella applications from compiling
  * `--skip-local-deps` - skips non-remote dependencies, such as path deps, from compiling

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*Consult [api-reference.md](api-reference.md) for complete listing*