# Find wide compile dependencies with `mix xref graph`

When a small change recompiles a large part of an application, `mix xref graph` can show which file has the widest compile-time reach.

```bash
# Show files with the most compile-time dependents.
mix xref graph --format stats --label compile-connected

Top 10 files with most incoming dependencies:
  lib/my_app_web.ex (187)
  lib/my_app/repo.ex (54)
  lib/my_app_web/components/core_components.ex (31)
```

The `compile-connected` label includes transitive compile dependencies, so the stats show how many files may need recompiling after a given file changes.

Macros commonly create these dependencies through `use`, `require`, and macro imports. Code evaluated in a module body can create them as well. An ordinary remote function call inside a function body is a runtime dependency instead.

Use `--sink` or `--source` to inspect a file from either direction:

```bash
# Files with a path to my_app_web.ex.
mix xref graph --sink lib/my_app_web.ex --label compile-connected

# Files referenced by this LiveView.
mix xref graph --source lib/my_app_web/live/post_live/index.ex
```

In a Phoenix application, `lib/my_app_web.ex` often appears near the top because controllers, components, and LiveViews all `use` it.

Keep those quoted definitions small and stable. Helpers that change often are usually better placed in an ordinary module:

```elixir
# Editing this quoted helper can recompile every module that uses it.
defmodule MyAppWeb do
  def live_view do
    quote do
      use Phoenix.LiveView

      def page_title(suffix), do: "#{suffix} · MyApp"
    end
  end
end

# Keep the implementation in a regular module.
defmodule MyAppWeb do
  def live_view do
    quote do
      use Phoenix.LiveView

      import MyAppWeb.PageHelpers
    end
  end
end
```

The same task can also find compile cycles and produce a Graphviz file:

```bash
# List compile-time cycles.
mix xref graph --format cycles --label compile-connected

# Render the graph as an image.
mix xref graph --format dot --label compile-connected
dot -Tpng xref_graph.dot -o xref_graph.png
```

Calls to `Application.compile_env/3` are another source of compile-time dependencies, so they are worth checking in files with a large reach.

[mix xref docs](https://hexdocs.pm/mix/Mix.Tasks.Xref.html)


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Created by: almirsarajcic
Date: August 15, 2026
URL: https://elixirdrops.net/d/B9qxNc8h