diff --git a/lib/pinchflat/downloading/downloading_helpers.ex b/lib/pinchflat/downloading/downloading_helpers.ex
index a7f64e3..01c2393 100644
--- a/lib/pinchflat/downloading/downloading_helpers.ex
+++ b/lib/pinchflat/downloading/downloading_helpers.ex
@@ -12,6 +12,7 @@ defmodule Pinchflat.Downloading.DownloadingHelpers do
   alias Pinchflat.Tasks
   alias Pinchflat.Sources.Source
   alias Pinchflat.Media.MediaItem
+  alias Pinchflat.Media.MediaQuery
   alias Pinchflat.Downloading.MediaDownloadWorker
 
   @doc """
@@ -64,4 +65,27 @@ defmodule Pinchflat.Downloading.DownloadingHelpers do
       {:error, :should_not_download}
     end
   end
+
+  @doc """
+  For a given source, enqueues download jobs for all media items _that have already been downloaded_.
+
+  This is useful for when a source's download settings have changed and you want to run through all
+  existing media and retry the download. For instance, if the source didn't originally download thumbnails
+  and you've changed the source to download them, you can use this to download all the thumbnails for
+  existing media items.
+
+  NOTE: does not delete existing files whatsoever. Will cause a full redownload of everything if the
+  output template has changed.
+
+  Returns [{:ok, %Task{}} | {:error, any()}]
+  """
+  def kickoff_redownload_for_existing_media(%Source{} = source) do
+    MediaQuery.new()
+    |> MediaQuery.for_source(source)
+    |> MediaQuery.with_media_downloaded_at()
+    |> MediaQuery.where_download_not_prevented()
+    |> MediaQuery.where_not_culled()
+    |> Repo.all()
+    |> Enum.map(&MediaDownloadWorker.kickoff_with_task/1)
+  end
 end
diff --git a/lib/pinchflat/downloading/media_download_worker.ex b/lib/pinchflat/downloading/media_download_worker.ex
index aa3e86c..7bd7fe9 100644
--- a/lib/pinchflat/downloading/media_download_worker.ex
+++ b/lib/pinchflat/downloading/media_download_worker.ex
@@ -44,6 +44,8 @@ defmodule Pinchflat.Downloading.MediaDownloadWorker do
   @impl Oban.Worker
   def perform(%Oban.Job{args: %{"id" => media_item_id} = args}) do
     should_force = Map.get(args, "force", false)
+    # TODO: rename to `upgrade_quality?` or similar to disambiguate from the other redownload method
+    # that doesn't `force_overwrites`
     is_redownload = Map.get(args, "redownload?", false)
 
     media_item =
diff --git a/lib/pinchflat/media/media_query.ex b/lib/pinchflat/media/media_query.ex
index 3fe57d4..0fadc26 100644
--- a/lib/pinchflat/media/media_query.ex
+++ b/lib/pinchflat/media/media_query.ex
@@ -12,6 +12,15 @@ defmodule Pinchflat.Media.MediaQuery do
 
   alias Pinchflat.Media.MediaItem
 
+  # TODO: test
+  defmacro __using__(_opts) do
+    quote do
+      import Ecto.Query, warn: false
+
+      alias unquote(__MODULE__)
+    end
+  end
+
   # Prefixes:
   # - for_* - belonging to a certain record
   # - join_* - for joining on a certain record
diff --git a/test/pinchflat/downloading/downloading_helpers_test.exs b/test/pinchflat/downloading/downloading_helpers_test.exs
index 5148e50..f8bc2ae 100644
--- a/test/pinchflat/downloading/downloading_helpers_test.exs
+++ b/test/pinchflat/downloading/downloading_helpers_test.exs
@@ -110,4 +110,32 @@ defmodule Pinchflat.Downloading.DownloadingHelpersTest do
       refute_enqueued(worker: MediaDownloadWorker)
     end
   end
+
+  describe "kickoff_redownload_for_existing_media/1" do
+    test "enqueues a download job for each downloaded media item" do
+      source = source_fixture()
+      media_item = media_item_fixture(source_id: source.id, media_downloaded_at: DateTime.utc_now())
+
+      assert [{:ok, _}] = DownloadingHelpers.kickoff_redownload_for_existing_media(source)
+
+      assert_enqueued(worker: MediaDownloadWorker, args: %{"id" => media_item.id})
+    end
+
+    test "doesn't enqueue jobs for media that should be ignored" do
+      source = source_fixture()
+      other_source = source_fixture()
+      _not_downloaded = media_item_fixture(source_id: source.id, media_downloaded_at: nil)
+      _other_source = media_item_fixture(source_id: other_source.id, media_downloaded_at: DateTime.utc_now())
+
+      _download_prevented =
+        media_item_fixture(source_id: source.id, media_downloaded_at: DateTime.utc_now(), prevent_download: true)
+
+      _culled =
+        media_item_fixture(source_id: source.id, media_downloaded_at: DateTime.utc_now(), culled_at: DateTime.utc_now())
+
+      assert [] = DownloadingHelpers.kickoff_redownload_for_existing_media(source)
+
+      refute_enqueued(worker: MediaDownloadWorker)
+    end
+  end
 end