diff --git a/lib/oci/registry.ex b/lib/oci/registry.ex
index 2d26f49..c0a81d7 100644
--- a/lib/oci/registry.ex
+++ b/lib/oci/registry.ex
@@ -6,6 +6,21 @@ defmodule OCI.Registry do
 
   use TypedStruct
 
+  @typedoc "Repository name, e.g. `\"myorg/myrepo\"`"
+  @type repo_t :: String.t()
+
+  @typedoc "Content-addressable digest, e.g. `\"sha256:abc123...\"`"
+  @type digest_t :: String.t()
+
+  @typedoc "A tag or digest used to identify a manifest"
+  @type reference_t :: String.t()
+
+  @typedoc "Human-readable tag, e.g. `\"latest\"` or `\"v1.0.0\"`"
+  @type tag_t :: String.t()
+
+  @typedoc "Upload session identifier (UUID)"
+  @type uuid_t :: String.t()
+
   @repo_name_pattern ~r/^([a-z0-9]+(?:[._-][a-z0-9]+)*)(\/[a-z0-9]+(?:[._-][a-z0-9]+)*)*$/
 
   typedstruct do
@@ -64,8 +79,8 @@ defmodule OCI.Registry do
     adapter(auth).challenge(registry)
   end
 
-  @spec validate_repository_name(registry :: t(), repo :: String.t()) ::
-          {:ok, repo :: String.t()} | {:error, :NAME_INVALID, String.t()}
+  @spec validate_repository_name(registry :: t(), repo :: repo_t()) ::
+          {:ok, repo :: repo_t()} | {:error, :NAME_INVALID, String.t()}
 
   def validate_repository_name(registry, repo) do
     if Regex.match?(registry.repo_name_pattern, repo) do
@@ -329,7 +344,7 @@ defmodule OCI.Registry do
       iex> OCI.Registry.verify_digest("hello", "invalid-digest")
       {:error, :DIGEST_INVALID, %{digest: "invalid-digest", msg: "Invalid digest format"}}
   """
-  @spec verify_digest(binary(), String.t()) :: :ok | {:error, :DIGEST_INVALID, map()}
+  @spec verify_digest(binary(), digest_t()) :: :ok | {:error, :DIGEST_INVALID, map()}
   def verify_digest(data, digest) do
     case digest do
       "sha256:" <> hash ->
@@ -376,7 +391,7 @@ defmodule OCI.Registry do
       iex> OCI.Registry.blobs_digest_path("myrepo", "sha256:abc123")
       "/v2/myrepo/blobs/sha256:abc123"
   """
-  @spec blobs_digest_path(String.t(), String.t()) :: String.t()
+  @spec blobs_digest_path(repo_t(), digest_t()) :: String.t()
   def blobs_digest_path(repo, digest) do
     "/#{api_version()}/#{repo}/blobs/#{digest}"
   end
@@ -395,7 +410,7 @@ defmodule OCI.Registry do
       iex> OCI.Registry.manifests_reference_path("library/alpine", "sha256:24dda0a1be6293020e5355d4a09b9a8bb72a8b44c27b0ca8560669b8ed52d3ec")
       "/v2/library/alpine/manifests/sha256:24dda0a1be6293020e5355d4a09b9a8bb72a8b44c27b0ca8560669b8ed52d3ec"
   """
-  @spec manifests_reference_path(String.t(), String.t()) :: String.t()
+  @spec manifests_reference_path(repo_t(), reference_t()) :: String.t()
   def manifests_reference_path(repo, reference) do
     "/#{api_version()}/#{repo}/manifests/#{reference}"
   end
@@ -411,7 +426,7 @@ defmodule OCI.Registry do
       iex> OCI.Registry.blobs_uploads_path("myrepo", "123e4567-e89b-12d3-a456-426614174000")
       "/v2/myrepo/blobs/uploads/123e4567-e89b-12d3-a456-426614174000"
   """
-  @spec blobs_uploads_path(String.t(), String.t()) :: String.t()
+  @spec blobs_uploads_path(repo_t(), uuid_t()) :: String.t()
   def blobs_uploads_path(repo, uuid) do
     "/#{api_version()}/#{repo}/blobs/uploads/#{uuid}"
   end
diff --git a/lib/oci/storage/adapter.ex b/lib/oci/storage/adapter.ex
index 8c14dec..9c6c7bf 100644
--- a/lib/oci/storage/adapter.ex
+++ b/lib/oci/storage/adapter.ex
@@ -35,6 +35,8 @@ defmodule OCI.Storage.Adapter do
   ```
   """
 
+  alias OCI.Registry
+
   @type t :: struct()
 
   @type error_details_t :: any()
@@ -44,8 +46,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback blob_exists?(
               storage :: t(),
-              repo :: String.t(),
-              digest :: String.t(),
+              repo :: Registry.repo_t(),
+              digest :: Registry.digest_t(),
               ctx :: OCI.Context.t()
             ) ::
               boolean()
@@ -55,8 +57,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback cancel_blob_upload(
               storage :: t(),
-              repo :: String.t(),
-              uuid :: String.t(),
+              repo :: Registry.repo_t(),
+              uuid :: Registry.uuid_t(),
               ctx :: OCI.Context.t()
             ) ::
               :ok
@@ -68,9 +70,9 @@ defmodule OCI.Storage.Adapter do
   """
   @callback complete_blob_upload(
               storage :: t(),
-              repo :: String.t(),
-              upload_id :: String.t(),
-              digest :: String.t(),
+              repo :: Registry.repo_t(),
+              upload_id :: Registry.uuid_t(),
+              digest :: Registry.digest_t(),
               ctx :: OCI.Context.t()
             ) ::
               :ok | {:error, atom()} | {:error, atom(), error_details_t}
@@ -80,8 +82,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback delete_blob(
               storage :: t(),
-              repo :: String.t(),
-              digest :: String.t(),
+              repo :: Registry.repo_t(),
+              digest :: Registry.digest_t(),
               ctx :: OCI.Context.t()
             ) ::
               :ok | {:error, :BLOB_UNKNOWN} | {:error, :BLOB_UNKNOWN, error_details_t}
@@ -91,8 +93,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback delete_manifest(
               storage :: t(),
-              repo :: String.t(),
-              reference :: String.t(),
+              repo :: Registry.repo_t(),
+              reference :: Registry.reference_t(),
               ctx :: OCI.Context.t()
             ) ::
               :ok | {:error, atom()}
@@ -102,8 +104,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback get_blob(
               storage :: t(),
-              repo :: String.t(),
-              digest :: String.t(),
+              repo :: Registry.repo_t(),
+              digest :: Registry.digest_t(),
               ctx :: OCI.Context.t()
             ) ::
               {:ok, content :: binary()}
@@ -115,8 +117,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback get_manifest(
               storage :: t(),
-              repo :: String.t(),
-              reference :: String.t(),
+              repo :: Registry.repo_t(),
+              reference :: Registry.reference_t(),
               ctx :: OCI.Context.t()
             ) ::
               {:ok, manifest :: binary(), content_type :: String.t()}
@@ -127,8 +129,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback get_blob_upload_status(
               storage :: t(),
-              repo :: String.t(),
-              uuid :: String.t(),
+              repo :: Registry.repo_t(),
+              uuid :: Registry.uuid_t(),
               ctx :: OCI.Context.t()
             ) ::
               {:ok, range :: String.t()} | {:error, term()} | {:error, term(), error_details_t}
@@ -138,8 +140,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback get_blob_upload_offset(
               storage :: t(),
-              repo :: String.t(),
-              uuid :: String.t(),
+              repo :: Registry.repo_t(),
+              uuid :: Registry.uuid_t(),
               ctx :: OCI.Context.t()
             ) ::
               {:ok, size :: non_neg_integer()}
@@ -151,8 +153,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback manifest_exists?(
               storage :: t(),
-              repo :: String.t(),
-              reference :: String.t(),
+              repo :: Registry.repo_t(),
+              reference :: Registry.reference_t(),
               ctx :: OCI.Context.t()
             ) ::
               boolean()
@@ -166,8 +168,12 @@ defmodule OCI.Storage.Adapter do
   @doc """
   Initiates a blob upload session.
   """
-  @callback initiate_blob_upload(storage :: t(), repo :: String.t(), ctx :: OCI.Context.t()) ::
-              {:ok, upload_id :: String.t()}
+  @callback initiate_blob_upload(
+              storage :: t(),
+              repo :: Registry.repo_t(),
+              ctx :: OCI.Context.t()
+            ) ::
+              {:ok, upload_id :: Registry.uuid_t()}
               | {:error, term()}
               | {:error, term(), error_details_t}
 
@@ -176,11 +182,11 @@ defmodule OCI.Storage.Adapter do
   """
   @callback list_tags(
               storage :: t(),
-              repo :: String.t(),
+              repo :: Registry.repo_t(),
               pagination :: OCI.Pagination.t(),
               ctx :: OCI.Context.t()
             ) ::
-              {:ok, tags :: [String.t()]}
+              {:ok, tags :: [Registry.tag_t()]}
               | {:error, :NAME_UNKNOWN}
               | {:error, :NAME_UNKNOWN, error_details_t}
 
@@ -189,9 +195,9 @@ defmodule OCI.Storage.Adapter do
   """
   @callback mount_blob(
               storage :: t(),
-              repo :: String.t(),
-              digest :: String.t(),
-              from_repo :: String.t(),
+              repo :: Registry.repo_t(),
+              digest :: Registry.digest_t(),
+              from_repo :: Registry.repo_t(),
               ctx :: OCI.Context.t()
             ) ::
               :ok | {:error, :BLOB_UNKNOWN} | {:error, :BLOB_UNKNOWN, error_details_t}
@@ -201,10 +207,10 @@ defmodule OCI.Storage.Adapter do
   """
   @callback store_manifest(
               storage :: t(),
-              repo :: String.t(),
-              reference :: String.t(),
+              repo :: Registry.repo_t(),
+              reference :: Registry.reference_t(),
               manifest :: map(),
-              manifest_digest :: String.t(),
+              manifest_digest :: Registry.digest_t(),
               ctx :: OCI.Context.t()
             ) ::
               :ok
@@ -214,15 +220,16 @@ defmodule OCI.Storage.Adapter do
   @doc """
   Checks if a repository exists.
   """
-  @callback repo_exists?(storage :: t(), repo :: String.t(), ctx :: OCI.Context.t()) :: boolean()
+  @callback repo_exists?(storage :: t(), repo :: Registry.repo_t(), ctx :: OCI.Context.t()) ::
+              boolean()
 
   @doc """
   Uploads a chunk of data to an ongoing blob upload.
   """
   @callback upload_blob_chunk(
               storage :: t(),
-              repo :: String.t(),
-              uuid :: String.t(),
+              repo :: Registry.repo_t(),
+              uuid :: Registry.uuid_t(),
               chunk :: binary(),
               content_range :: String.t(),
               ctx :: OCI.Context.t()
@@ -239,8 +246,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback list_referrers(
               storage :: t(),
-              repo :: String.t(),
-              subject_digest :: String.t(),
+              repo :: Registry.repo_t(),
+              subject_digest :: Registry.digest_t(),
               filters :: map(),
               ctx :: OCI.Context.t()
             ) ::
@@ -251,8 +258,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback put_referrer(
               storage :: t(),
-              repo :: String.t(),
-              subject_digest :: String.t(),
+              repo :: Registry.repo_t(),
+              subject_digest :: Registry.digest_t(),
               descriptor :: map(),
               ctx :: OCI.Context.t()
             ) ::
@@ -263,8 +270,8 @@ defmodule OCI.Storage.Adapter do
   """
   @callback upload_exists?(
               storage :: t(),
-              repo :: String.t(),
-              uuid :: String.t(),
+              repo :: Registry.repo_t(),
+              uuid :: Registry.uuid_t(),
               ctx :: OCI.Context.t()
             ) ::
               boolean()