diff --git a/lib/waffle/behaviors/storage_behaviour.ex b/lib/waffle/behaviors/storage_behaviour.ex
new file mode 100644
index 0000000..e318a12
--- /dev/null
+++ b/lib/waffle/behaviors/storage_behaviour.ex
@@ -0,0 +1,7 @@
+defmodule Waffle.StorageBehavior do
+  @callback put(definition :: atom, version :: atom, file_and_scope :: {Waffle.File.t(), term}) :: {:ok, file_name :: String.t()} | {:error, reason :: term}
+
+  @callback url(definition :: atom, version :: atom, file_and_scope :: {Waffle.File.t(), term}) :: String.t()
+
+  @callback delete(definition :: atom, version :: atom, file_and_scope :: {Waffle.File.t(), term}) :: atom
+end
diff --git a/lib/waffle/storage/local.ex b/lib/waffle/storage/local.ex
index 2a3c1e4..a2dda10 100644
--- a/lib/waffle/storage/local.ex
+++ b/lib/waffle/storage/local.ex
@@ -22,8 +22,11 @@ defmodule Waffle.Storage.Local do
       end
   """
 
+  @behaviour Waffle.StorageBehavior
+
   alias Waffle.Definition.Versioning
 
+  @impl true
   def put(definition, version, {file, scope}) do
     destination_path = Path.join([
       definition.storage_dir_prefix(),
@@ -41,6 +44,7 @@ defmodule Waffle.Storage.Local do
     {:ok, file.file_name}
   end
 
+  @impl true
   def url(definition, version, file_and_scope, _options \\ []) do
     local_path = Path.join([
       definition.storage_dir(version, file_and_scope),
@@ -56,6 +60,7 @@ defmodule Waffle.Storage.Local do
     |> URI.encode()
   end
 
+  @impl true
   def delete(definition, version, file_and_scope) do
     Path.join([
       definition.storage_dir_prefix(),
diff --git a/lib/waffle/storage/s3.ex b/lib/waffle/storage/s3.ex
index c84ab9a..8d02ee2 100644
--- a/lib/waffle/storage/s3.ex
+++ b/lib/waffle/storage/s3.ex
@@ -130,6 +130,8 @@ defmodule Waffle.Storage.S3 do
   """
   require Logger
 
+  @behaviour Waffle.StorageBehavior
+
   alias ExAws.Config
   alias ExAws.Request.Url
   alias ExAws.S3
@@ -138,6 +140,7 @@ defmodule Waffle.Storage.S3 do
 
   @default_expiry_time 60 * 5
 
+  @impl true
   def put(definition, version, {file, scope}) do
     destination_dir = definition.storage_dir(version, {file, scope})
     s3_bucket = s3_bucket(definition, {file, scope})
@@ -152,6 +155,7 @@ defmodule Waffle.Storage.S3 do
     do_put(file, {s3_bucket, s3_key, s3_options})
   end
 
+  @impl true
   def url(definition, version, file_and_scope, options \\ []) do
     case Keyword.get(options, :signed, false) do
       false -> build_url(definition, version, file_and_scope, options)
@@ -159,6 +163,7 @@ defmodule Waffle.Storage.S3 do
     end
   end
 
+  @impl true
   def delete(definition, version, {file, scope}) do
     s3_bucket(definition, {file, scope})
     |> S3.delete_object(s3_key(definition, version, {file, scope}))