diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9e617a7..2f60178 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+- Read runtime icons from the manifests of every loaded application, so libraries can ship `priv/iconify/manifest.json` with the icons their components use. The application's own manifest wins when two define the same icon; the compiler and mix tasks still read and write only the project's own manifest. `PhoenixIconify.Manifest.read_all/1` and `manifest_paths/0` expose the merged view.
+- `PhoenixIconify.Manifest.add_icon/3` with `persist: true` writes the application's own manifest plus the new icon, not the merged runtime set.
+
 ## v0.3.6
 
 - Fetch icons that a cached icon set lacks from the Iconify API. A set cached before an icon was added to the collection made new icons fail with "Icon not found" (#2).
diff --git a/README.md b/README.md
index 7d81f54..8c74631 100644
--- a/README.md
+++ b/README.md
@@ -225,6 +225,18 @@ mix phoenix_iconify.cache list
 mix phoenix_iconify.cache clear
 ```
 
+## Icons in libraries
+
+A library can use icons in its own components, and they reach the application without any configuration there. Add the compiler to the library's `mix.exs` as above, and ship its manifest in the Hex package:
+
+```elixir
+defp package do
+  [files: ~w(lib priv/iconify/manifest.json mix.exs README.md LICENSE)]
+end
+```
+
+Commit `priv/iconify/manifest.json`, so applications compiling the library never fetch icons. At runtime, icons are read from the manifests of every loaded application; when two define the same icon, the application's own manifest wins. The compiler and the `mix phoenix_iconify.*` tasks only ever read and write the current project's own manifest.
+
 ## Volt projects
 
 For projects created with [Volt](https://hex.pm/packages/volt), PhoenixIconify is the server-rendered option:
diff --git a/lib/phoenix_iconify/manifest.ex b/lib/phoenix_iconify/manifest.ex
index d679ae7..48718f4 100644
--- a/lib/phoenix_iconify/manifest.ex
+++ b/lib/phoenix_iconify/manifest.ex
@@ -3,6 +3,13 @@ defmodule PhoenixIconify.Manifest do
   Manages the icon manifest stored in priv/.
 
   The manifest contains all discovered icons, cached between compilations.
+
+  Each application compiled with the `:phoenix_iconify` compiler writes its
+  own manifest. At runtime, icons are read from the manifests of every
+  loaded application, so a library that ships `priv/iconify/manifest.json`
+  brings its icons along; the application's own manifest wins when two
+  define the same icon. The compiler and the mix tasks read and write only
+  the application's own manifest.
   """
 
   @manifest_filename "manifest.json"
@@ -50,12 +57,45 @@ defmodule PhoenixIconify.Manifest do
   end
 
   @doc """
-  Gets icons from the manifest, loading from persistent storage on first use.
+  Reads and merges the manifests at `paths`, later ones winning.
+
+  Defaults to `manifest_paths/0`: the manifests of loaded libraries, then
+  the application's own.
+  """
+  @spec read_all([Path.t()]) :: %{String.t() => Iconify.Icon.t()}
+  def read_all(paths \\ manifest_paths()) do
+    Enum.reduce(paths, %{}, fn path, icons -> Map.merge(icons, read(path)) end)
+  end
+
+  @doc """
+  Returns the manifests runtime icons come from: those shipped by loaded
+  applications, sorted by application, followed by the application's own
+  manifest, which may not exist yet.
+  """
+  @spec manifest_paths() :: [Path.t()]
+  def manifest_paths do
+    own = manifest_path()
+
+    # Applications without a code path have no priv directory of their own.
+    libraries =
+      for app <- loaded_apps(),
+          priv = :code.priv_dir(app),
+          is_list(priv),
+          path = Path.join([List.to_string(priv), "iconify", @manifest_filename]),
+          path != own and File.regular?(path),
+          do: path
+
+    libraries ++ [own]
+  end
+
+  @doc """
+  Gets icons from every loaded manifest, loading from persistent storage on
+  first use.
   """
   def get_icons do
     case :persistent_term.get({__MODULE__, :icons}, nil) do
       nil ->
-        icons = read()
+        icons = read_all()
         :persistent_term.put({__MODULE__, :icons}, icons)
         icons
 
@@ -68,7 +108,7 @@ defmodule PhoenixIconify.Manifest do
   Reloads icons from disk into persistent_term.
   """
   def reload do
-    icons = read()
+    icons = read_all()
     :persistent_term.put({__MODULE__, :icons}, icons)
     icons
   end
@@ -84,11 +124,12 @@ defmodule PhoenixIconify.Manifest do
   Adds an icon to the runtime cache and optionally persists to disk.
   """
   def add_icon(name, %Iconify.Icon{} = icon, opts \\ []) do
-    updated = Map.put(get_icons(), name, %{icon | name: name})
-    :persistent_term.put({__MODULE__, :icons}, updated)
+    icon = %{icon | name: name}
+    :persistent_term.put({__MODULE__, :icons}, Map.put(get_icons(), name, icon))
 
+    # Only the application's own manifest, never icons from its libraries.
     if Keyword.get(opts, :persist, false) do
-      write(updated)
+      write(Map.put(read(), name, icon))
     end
 
     :ok
@@ -109,12 +150,16 @@ defmodule PhoenixIconify.Manifest do
   end
 
   defp discover_manifest_path do
+    loaded_apps()
+    |> Enum.map(&Path.join([priv_dir(&1), "iconify", @manifest_filename]))
+    |> Enum.find(&File.regular?/1)
+  end
+
+  defp loaded_apps do
     :application.loaded_applications()
     |> Enum.map(fn {app, _description, _version} -> app end)
-    |> Enum.sort()
     |> Enum.reject(&(&1 in [:phoenix_iconify, :iconify]))
-    |> Enum.map(&Path.join([priv_dir(&1), "iconify", @manifest_filename]))
-    |> Enum.find(&File.regular?/1)
+    |> Enum.sort()
   end
 
   defp mix_project_app do
diff --git a/test/phoenix_iconify/library_manifests_test.exs b/test/phoenix_iconify/library_manifests_test.exs
new file mode 100644
index 0000000..229c662
--- /dev/null
+++ b/test/phoenix_iconify/library_manifests_test.exs
@@ -0,0 +1,106 @@
+defmodule PhoenixIconify.LibraryManifestsTest do
+  # Loads applications and changes :otp_app and the cached icons, all node-wide.
+  use ExUnit.Case, async: false
+
+  alias PhoenixIconify.Manifest
+
+  @moduletag :tmp_dir
+
+  defp icon(name, body), do: %Iconify.Icon{name: name, body: body, width: 24, height: 24}
+
+  # An application on the code path with its own priv/iconify/manifest.json,
+  # as a library compiled with the :phoenix_iconify compiler ships it. The
+  # directory is named after the application so :code.priv_dir/1 finds it.
+  defp load_app(tmp_dir, icons) do
+    app = :"iconify_fixture_#{System.unique_integer([:positive])}"
+    dir = Path.join(tmp_dir, Atom.to_string(app))
+    ebin = Path.join(dir, "ebin")
+    File.mkdir_p!(ebin)
+
+    spec = {:application, app, [vsn: ~c"1.0.0", modules: [], applications: []]}
+    File.write!(Path.join(ebin, "#{app}.app"), :io_lib.format(~c"~p.~n", [spec]))
+
+    if icons != %{},
+      do: Manifest.write(icons, Path.join([dir, "priv", "iconify", "manifest.json"]))
+
+    true = Code.prepend_path(ebin)
+    :ok = Application.load(app)
+
+    on_exit(fn ->
+      Application.unload(app)
+      Code.delete_path(ebin)
+    end)
+
+    app
+  end
+
+  defp use_own_app(app) do
+    previous = Application.get_env(:phoenix_iconify, :otp_app)
+    Application.put_env(:phoenix_iconify, :otp_app, app)
+    Manifest.clear_cache()
+
+    on_exit(fn ->
+      Manifest.clear_cache()
+
+      if previous,
+        do: Application.put_env(:phoenix_iconify, :otp_app, previous),
+        else: Application.delete_env(:phoenix_iconify, :otp_app)
+    end)
+  end
+
+  test "read_all/1 merges manifests, later ones winning", %{tmp_dir: tmp_dir} do
+    library = Path.join(tmp_dir, "library.json")
+    own = Path.join(tmp_dir, "own.json")
+
+    Manifest.write(
+      %{"lucide:a" => icon("lucide:a", "lib"), "lucide:b" => icon("lucide:b", "lib")},
+      library
+    )
+
+    Manifest.write(%{"lucide:b" => icon("lucide:b", "own")}, own)
+
+    icons = Manifest.read_all([library, own, Path.join(tmp_dir, "missing.json")])
+
+    assert icons["lucide:a"].body == "lib"
+    assert icons["lucide:b"].body == "own"
+  end
+
+  test "runtime icons include loaded libraries', the application's own winning", %{
+    tmp_dir: tmp_dir
+  } do
+    library =
+      load_app(tmp_dir, %{
+        "lucide:shared" => icon("lucide:shared", "library"),
+        "lucide:only-lib" => icon("lucide:only-lib", "l")
+      })
+
+    own = load_app(tmp_dir, %{"lucide:shared" => icon("lucide:shared", "own")})
+    use_own_app(own)
+
+    paths = Manifest.manifest_paths()
+
+    library_path =
+      Path.join([List.to_string(:code.priv_dir(library)), "iconify", "manifest.json"])
+
+    assert library_path in paths
+    assert List.last(paths) == Manifest.manifest_path()
+
+    icons = Manifest.get_icons()
+    assert icons["lucide:only-lib"].body == "l"
+    assert icons["lucide:shared"].body == "own"
+    assert PhoenixIconify.icon_exists?("lucide:only-lib")
+  end
+
+  test "add_icon/3 persists only the application's own icons", %{tmp_dir: tmp_dir} do
+    load_app(tmp_dir, %{"lucide:from-lib" => icon("lucide:from-lib", "l")})
+    own = load_app(tmp_dir, %{})
+    use_own_app(own)
+
+    assert Map.has_key?(Manifest.get_icons(), "lucide:from-lib")
+
+    :ok = Manifest.add_icon("lucide:new", icon("lucide:new", "n"), persist: true)
+
+    assert Map.keys(Manifest.read()) == ["lucide:new"]
+    assert Map.has_key?(Manifest.get_icons(), "lucide:from-lib")
+  end
+end