diff --git a/lib/federation/activity_pub/utils.ex b/lib/federation/activity_pub/utils.ex
index 0cfab57e3..528fa14b5 100644
--- a/lib/federation/activity_pub/utils.ex
+++ b/lib/federation/activity_pub/utils.ex
@@ -25,11 +25,13 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
 
   # Some implementations send the actor URI as the actor field, others send the entire actor object,
   # so figure out what the actor's URI is based on what we have.
+  @spec get_url(map() | String.t() | list(String.t()) | any()) :: String.t() | nil
   def get_url(%{"id" => id}), do: id
   def get_url(id) when is_binary(id), do: id
   def get_url(ids) when is_list(ids), do: get_url(hd(ids))
   def get_url(_), do: nil
 
+  @spec make_json_ld_header :: map()
   def make_json_ld_header do
     %{
       "@context" => [
@@ -99,6 +101,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
     }
   end
 
+  @spec make_date :: String.t()
   def make_date do
     DateTime.utc_now() |> DateTime.truncate(:second) |> DateTime.to_iso8601()
   end
@@ -130,6 +133,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
   Applies to activities sent by group members from outside this instance to a group of this instance,
   we then need to relay (`Announce`) the object to other members on other instances.
   """
+  @spec maybe_relay_if_group_activity(Activity.t(), Actor.t() | nil | list(Actor.t())) :: :ok
   def maybe_relay_if_group_activity(activity, attributed_to \\ nil)
 
   def maybe_relay_if_group_activity(
@@ -153,6 +157,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
     :ok
   end
 
+  @spec do_maybe_relay_if_group_activity(map(), list(String.t()) | String.t()) :: :ok
   defp do_maybe_relay_if_group_activity(object, attributed_to) when is_list(attributed_to),
     do: do_maybe_relay_if_group_activity(object, hd(attributed_to))
 
@@ -199,6 +204,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
   Adds an id and a published data if they aren't there,
   also adds it to an included object
   """
+  @spec lazy_put_activity_defaults(map()) :: map()
   def lazy_put_activity_defaults(%{"object" => _object} = map) do
     if is_map(map["object"]) do
       object = lazy_put_object_defaults(map["object"])
@@ -215,6 +221,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
     Map.put_new_lazy(map, "published", &make_date/0)
   end
 
+  @spec get_actor(map()) :: String.t() | nil
   def get_actor(%{"actor" => actor}) when is_binary(actor) do
     actor
   end
@@ -242,6 +249,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
 
   Takes the actor or attributedTo attributes (considers only the first elem if they're an array)
   """
+  @spec origin_check?(String.t(), map()) :: boolean()
   def origin_check?(id, %{"type" => "Tombstone", "id" => tombstone_id}), do: id == tombstone_id
 
   def origin_check?(id, %{"actor" => actor, "attributedTo" => _attributed_to} = params)
@@ -283,6 +291,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
     compare_uris?(uri_1, uri_2)
   end
 
+  @spec compare_uris?(URI.t(), URI.t()) :: boolean()
   defp compare_uris?(%URI{} = id_uri, %URI{} = other_uri),
     do: id_uri.host == other_uri.host && id_uri.port == other_uri.port
 
diff --git a/lib/graphql/error.ex b/lib/graphql/error.ex
index e6b87b2c8..561567c5b 100644
--- a/lib/graphql/error.ex
+++ b/lib/graphql/error.ex
@@ -8,11 +8,19 @@ defmodule Mobilizon.GraphQL.Error do
   alias Mobilizon.Web.Gettext, as: GettextBackend
   import Mobilizon.Web.Gettext, only: [dgettext: 2]
 
+  @type t :: %{code: atom(), message: String.t(), status_code: pos_integer(), field: atom()}
+
   defstruct [:code, :message, :status_code, :field]
 
+  @type error :: {:error, any()} | {:error, any(), any(), any()} | atom()
+
+  @doc """
+  Normalize an error to return `t`.
+  """
   # Error Tuples
   # ------------
   # Regular errors
+  @spec normalize(error | list(error) | String.t() | any()) :: t()
   def normalize({:error, reason}) do
     handle(reason)
   end
diff --git a/lib/mobilizon/actors/member.ex b/lib/mobilizon/actors/member.ex
index a79ab2c5b..34703c765 100644
--- a/lib/mobilizon/actors/member.ex
+++ b/lib/mobilizon/actors/member.ex
@@ -8,18 +8,19 @@ defmodule Mobilizon.Actors.Member do
   import Ecto.Changeset
 
   alias Mobilizon.Actors.{Actor, MemberRole}
+  alias Mobilizon.Actors.Member.Metadata
   alias Mobilizon.Web.Endpoint
 
   @type t :: %__MODULE__{
           role: MemberRole.t(),
           parent: Actor.t(),
-          actor: Actor.t()
+          actor: Actor.t(),
+          metadata: Metadata.t()
         }
 
   @required_attrs [:parent_id, :actor_id, :url]
   @optional_attrs [:role, :invited_by_id]
   @attrs @required_attrs ++ @optional_attrs
-  @metadata_attrs []
 
   @primary_key {:id, :binary_id, autogenerate: true}
   schema "members" do
@@ -27,9 +28,7 @@ defmodule Mobilizon.Actors.Member do
     field(:url, :string)
     field(:member_since, :utc_datetime)
 
-    embeds_one :metadata, Metadata, on_replace: :delete do
-      # TODO : Use this space to put notes when someone is invited / requested to join
-    end
+    embeds_one(:metadata, Metadata, on_replace: :delete)
 
     belongs_to(:invited_by, Actor)
     belongs_to(:parent, Actor)
@@ -63,7 +62,7 @@ defmodule Mobilizon.Actors.Member do
   def changeset(%__MODULE__{} = member, attrs) do
     member
     |> cast(attrs, @attrs)
-    |> cast_embed(:metadata, with: &metadata_changeset/2)
+    |> cast_embed(:metadata)
     |> ensure_url()
     |> update_member_since()
     |> validate_required(@required_attrs)
@@ -72,11 +71,6 @@ defmodule Mobilizon.Actors.Member do
     |> unique_constraint(:url, name: :members_url_index)
   end
 
-  defp metadata_changeset(schema, params) do
-    schema
-    |> cast(params, @metadata_attrs)
-  end
-
   # If there's a blank URL that's because we're doing the first insert
   @spec ensure_url(Ecto.Changeset.t()) :: Ecto.Changeset.t()
   defp ensure_url(%Ecto.Changeset{data: %__MODULE__{url: nil}} = changeset) do
diff --git a/lib/mobilizon/actors/member/metadata.ex b/lib/mobilizon/actors/member/metadata.ex
new file mode 100644
index 000000000..ad4a251d1
--- /dev/null
+++ b/lib/mobilizon/actors/member/metadata.ex
@@ -0,0 +1,27 @@
+defmodule Mobilizon.Actors.Member.Metadata do
+  @moduledoc """
+  Represents metadata on a membership
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @type t :: %__MODULE__{}
+
+  @required_attrs []
+
+  @optional_attrs []
+
+  @attrs @required_attrs ++ @optional_attrs
+
+  embedded_schema do
+    # TODO : Use this space to put notes when someone is invited / requested to join
+  end
+
+  @doc false
+  @spec changeset(t | Ecto.Schema.t(), map) :: Ecto.Changeset.t()
+  def changeset(schema, params) do
+    schema
+    |> cast(params, @attrs)
+  end
+end
diff --git a/lib/mobilizon/medias/media.ex b/lib/mobilizon/medias/media.ex
index bda41a9d9..224252a52 100644
--- a/lib/mobilizon/medias/media.ex
+++ b/lib/mobilizon/medias/media.ex
@@ -5,7 +5,7 @@ defmodule Mobilizon.Medias.Media do
 
   use Ecto.Schema
 
-  import Ecto.Changeset, only: [cast: 3, cast_embed: 2, cast_embed: 3]
+  import Ecto.Changeset, only: [cast: 3, cast_embed: 2]
 
   alias Mobilizon.Actors.Actor
   alias Mobilizon.Discussions.Comment
@@ -20,16 +20,12 @@ defmodule Mobilizon.Medias.Media do
           actor: Actor.t()
         }
 
-  @metadata_attrs [:height, :width, :blurhash]
+  @attrs [:actor_id]
 
   schema "medias" do
     embeds_one(:file, File, on_replace: :update)
 
-    embeds_one :metadata, Metadata, on_replace: :update do
-      field(:height, :integer)
-      field(:width, :integer)
-      field(:blurhash, :string)
-    end
+    embeds_one(:metadata, Metadata, on_replace: :update)
 
     belongs_to(:actor, Actor)
     has_many(:event_picture, Event, foreign_key: :picture_id)
@@ -45,15 +41,8 @@ defmodule Mobilizon.Medias.Media do
   @spec changeset(t | Ecto.Schema.t(), map) :: Ecto.Changeset.t()
   def changeset(%__MODULE__{} = media, attrs) do
     media
-    |> cast(attrs, [:actor_id])
+    |> cast(attrs, @attrs)
     |> cast_embed(:file)
-    |> cast_embed(:metadata, with: &metadata_changeset/2)
-  end
-
-  @doc false
-  @spec metadata_changeset(Metadata.t(), map) :: Ecto.Changeset.t()
-  def metadata_changeset(metadata, attrs) do
-    metadata
-    |> cast(attrs, @metadata_attrs)
+    |> cast_embed(:metadata)
   end
 end
diff --git a/lib/mobilizon/medias/media/metadata.ex b/lib/mobilizon/medias/media/metadata.ex
new file mode 100644
index 000000000..b2d947da9
--- /dev/null
+++ b/lib/mobilizon/medias/media/metadata.ex
@@ -0,0 +1,38 @@
+defmodule Mobilizon.Medias.Media.Metadata do
+  @moduledoc """
+  Represents a media metadata
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @type t :: %__MODULE__{
+          width: non_neg_integer(),
+          height: non_neg_integer(),
+          blurhash: String.t()
+        }
+
+  @required_attrs []
+
+  @optional_attrs [
+    :width,
+    :height,
+    :blurhash
+  ]
+
+  @attrs @required_attrs ++ @optional_attrs
+
+  @primary_key false
+  embedded_schema do
+    field(:height, :integer)
+    field(:width, :integer)
+    field(:blurhash, :string)
+  end
+
+  @doc false
+  @spec changeset(t | Ecto.Schema.t(), map) :: Ecto.Changeset.t()
+  def changeset(schema, params) do
+    schema
+    |> cast(params, @attrs)
+  end
+end
diff --git a/lib/mobilizon/resources/resource.ex b/lib/mobilizon/resources/resource.ex
index 5c1de9d37..83a84bfce 100644
--- a/lib/mobilizon/resources/resource.ex
+++ b/lib/mobilizon/resources/resource.ex
@@ -10,6 +10,7 @@ defmodule Mobilizon.Resources.Resource do
   import EctoEnum
   defenum(TypeEnum, folder: 0, link: 1, picture: 20, pad: 30, calc: 40, visio: 50)
   alias Mobilizon.Actors.Actor
+  alias Mobilizon.Resources.Resource.Metadata
 
   @type t :: %__MODULE__{
           title: String.t(),
@@ -17,7 +18,7 @@ defmodule Mobilizon.Resources.Resource do
           url: String.t(),
           resource_url: String.t(),
           type: atom(),
-          metadata: Mobilizon.Resources.Resource.Metadata.t(),
+          metadata: Metadata.t(),
           children: list(__MODULE__),
           parent: __MODULE__,
           actor: Actor.t(),
@@ -37,20 +38,7 @@ defmodule Mobilizon.Resources.Resource do
     field(:local, :boolean, default: true)
     field(:published_at, :utc_datetime)
 
-    embeds_one :metadata, Metadata, on_replace: :delete do
-      field(:type, :string)
-      field(:title, :string)
-      field(:description, :string)
-      field(:image_remote_url, :string)
-      field(:width, :integer)
-      field(:height, :integer)
-      field(:author_name, :string)
-      field(:author_url, :string)
-      field(:provider_name, :string)
-      field(:provider_url, :string)
-      field(:html, :string)
-      field(:favicon_url, :string)
-    end
+    embeds_one(:metadata, Metadata, on_replace: :delete)
 
     has_many(:children, __MODULE__, foreign_key: :parent_id)
     belongs_to(:parent, __MODULE__, type: :binary_id)
@@ -63,27 +51,13 @@ defmodule Mobilizon.Resources.Resource do
   @required_attrs [:title, :url, :actor_id, :creator_id, :type, :path, :published_at]
   @optional_attrs [:summary, :parent_id, :resource_url, :local]
   @attrs @required_attrs ++ @optional_attrs
-  @metadata_attrs [
-    :type,
-    :title,
-    :description,
-    :image_remote_url,
-    :width,
-    :height,
-    :author_name,
-    :author_url,
-    :provider_name,
-    :provider_url,
-    :html,
-    :favicon_url
-  ]
 
   @doc false
   @spec changeset(t | Ecto.Schema.t(), map) :: Ecto.Changeset.t()
   def changeset(resource, attrs) do
     resource
     |> cast(attrs, @attrs)
-    |> cast_embed(:metadata, with: &metadata_changeset/2)
+    |> cast_embed(:metadata)
     |> ensure_url(:resource)
     |> maybe_add_published_at()
     |> validate_resource_or_folder()
@@ -91,11 +65,6 @@ defmodule Mobilizon.Resources.Resource do
     |> unique_constraint(:url, name: :resource_url_index)
   end
 
-  defp metadata_changeset(schema, params) do
-    schema
-    |> cast(params, @metadata_attrs)
-  end
-
   @spec validate_resource_or_folder(Changeset.t()) :: Changeset.t()
   defp validate_resource_or_folder(%Changeset{} = changeset) do
     with {status, type} when status in [:changes, :data] <- fetch_field(changeset, :type),
diff --git a/lib/mobilizon/resources/resource/metadata.ex b/lib/mobilizon/resources/resource/metadata.ex
new file mode 100644
index 000000000..f8f66c8a6
--- /dev/null
+++ b/lib/mobilizon/resources/resource/metadata.ex
@@ -0,0 +1,64 @@
+defmodule Mobilizon.Resources.Resource.Metadata do
+  @moduledoc """
+  Represents a resource metadata
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @type t :: %__MODULE__{
+          type: String.t(),
+          title: String.t(),
+          image_remote_url: String.t(),
+          width: non_neg_integer(),
+          height: non_neg_integer(),
+          author_name: String.t(),
+          author_url: String.t(),
+          provider_name: String.t(),
+          provider_url: String.t(),
+          html: String.t(),
+          favicon_url: String.t()
+        }
+
+  @required_attrs []
+
+  @optional_attrs [
+    :type,
+    :title,
+    :description,
+    :image_remote_url,
+    :width,
+    :height,
+    :author_name,
+    :author_url,
+    :provider_name,
+    :provider_url,
+    :html,
+    :favicon_url
+  ]
+
+  @attrs @required_attrs ++ @optional_attrs
+
+  @primary_key false
+  embedded_schema do
+    field(:type, :string)
+    field(:title, :string)
+    field(:description, :string)
+    field(:image_remote_url, :string)
+    field(:width, :integer)
+    field(:height, :integer)
+    field(:author_name, :string)
+    field(:author_url, :string)
+    field(:provider_name, :string)
+    field(:provider_url, :string)
+    field(:html, :string)
+    field(:favicon_url, :string)
+  end
+
+  @doc false
+  @spec changeset(t | Ecto.Schema.t(), map) :: Ecto.Changeset.t()
+  def changeset(schema, params) do
+    schema
+    |> cast(params, @attrs)
+  end
+end
diff --git a/lib/mobilizon/users/setting.ex b/lib/mobilizon/users/setting.ex
index 9abb90754..6dab9b52d 100644
--- a/lib/mobilizon/users/setting.ex
+++ b/lib/mobilizon/users/setting.ex
@@ -6,6 +6,7 @@ defmodule Mobilizon.Users.Setting do
   use Ecto.Schema
   import Ecto.Changeset
   alias Mobilizon.Users.{NotificationPendingNotificationDelay, User}
+  alias Mobilizon.Users.Setting.Location
 
   @type t :: %__MODULE__{
           timezone: String.t(),
@@ -40,8 +41,6 @@ defmodule Mobilizon.Users.Setting do
 
   @attrs @required_attrs ++ @optional_attrs
 
-  @location_attrs [:name, :range, :geohash]
-
   @primary_key {:user_id, :id, autogenerate: false}
   schema "user_settings" do
     field(:timezone, :string)
@@ -60,11 +59,7 @@ defmodule Mobilizon.Users.Setting do
     field(:group_notifications, NotificationPendingNotificationDelay, default: :one_day)
     field(:last_notification_sent, :utc_datetime)
 
-    embeds_one :location, Location, on_replace: :update, primary_key: false do
-      field(:name, :string)
-      field(:range, :integer)
-      field(:geohash, :string)
-    end
+    embeds_one(:location, Location, on_replace: :update)
 
     belongs_to(:user, User, primary_key: true, type: :id, foreign_key: :id, define_field: false)
 
@@ -76,13 +71,7 @@ defmodule Mobilizon.Users.Setting do
   def changeset(setting, attrs) do
     setting
     |> cast(attrs, @attrs)
-    |> cast_embed(:location, with: &location_changeset/2)
+    |> cast_embed(:location)
     |> validate_required(@required_attrs)
   end
-
-  @spec location_changeset(location, map) :: Ecto.Changeset.t()
-  def location_changeset(schema, params) do
-    schema
-    |> cast(params, @location_attrs)
-  end
 end
diff --git a/lib/mobilizon/users/setting/location.ex b/lib/mobilizon/users/setting/location.ex
new file mode 100644
index 000000000..c403e2da6
--- /dev/null
+++ b/lib/mobilizon/users/setting/location.ex
@@ -0,0 +1,38 @@
+defmodule Mobilizon.Users.Setting.Location do
+  @moduledoc """
+  Represents user location information
+  """
+
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @type t :: %__MODULE__{
+          name: String.t(),
+          range: non_neg_integer(),
+          geohash: String.t()
+        }
+
+  @required_attrs []
+
+  @optional_attrs [
+    :name,
+    :range,
+    :geohash
+  ]
+
+  @attrs @required_attrs ++ @optional_attrs
+
+  @primary_key false
+  embedded_schema do
+    field(:name, :string)
+    field(:range, :integer)
+    field(:geohash, :string)
+  end
+
+  @doc false
+  @spec changeset(t | Ecto.Schema.t(), map) :: Ecto.Changeset.t()
+  def changeset(schema, params) do
+    schema
+    |> cast(params, @attrs)
+  end
+end
diff --git a/lib/web/plugs/http_security_plug.ex b/lib/web/plugs/http_security_plug.ex
index 8a278074d..938242462 100644
--- a/lib/web/plugs/http_security_plug.ex
+++ b/lib/web/plugs/http_security_plug.ex
@@ -62,9 +62,9 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
     static_url = Mobilizon.Web.Endpoint.static_url()
     websocket_url = Mobilizon.Web.Endpoint.websocket_url()
 
-    img_src = [@img_src | get_csp_config(:img_src, options)]
+    img_src = [@img_src] ++ [get_csp_config(:img_src, options)]
 
-    media_src = [@media_src | get_csp_config(:media_src, options)]
+    media_src = [@media_src] ++ [get_csp_config(:media_src, options)]
 
     connect_src = [
       @connect_src,
@@ -85,22 +85,22 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
         ]
       end
 
-    script_src = [script_src | get_csp_config(:script_src, options)]
+    script_src = [script_src] ++ [get_csp_config(:script_src, options)]
 
     style_src =
       if Config.get(:env) == :dev, do: [@style_src | "'unsafe-inline' "], else: @style_src
 
-    style_src = [style_src | get_csp_config(:style_src, options)]
+    style_src = [style_src] ++ [get_csp_config(:style_src, options)]
 
-    font_src = [@font_src | get_csp_config(:font_src, options)]
+    font_src = [@font_src] ++ [get_csp_config(:font_src, options)]
 
     frame_src = if Config.get(:env) == :dev, do: "frame-src 'self' ", else: "frame-src 'none' "
-    frame_src = [frame_src | get_csp_config(:frame_src, options)]
+    frame_src = [frame_src] ++ [get_csp_config(:frame_src, options)]
 
     frame_ancestors =
       if Config.get(:env) == :dev, do: "frame-ancestors 'self' ", else: "frame-ancestors 'none' "
 
-    frame_ancestors = [frame_ancestors | get_csp_config(:frame_ancestors, options)]
+    frame_ancestors = [frame_ancestors] ++ [get_csp_config(:frame_ancestors, options)]
 
     insecure = if scheme == "https", do: "upgrade-insecure-requests"
 
diff --git a/lib/web/plugs/set_locale_plug.ex b/lib/web/plugs/set_locale_plug.ex
index 0af554e13..fbfc371ea 100644
--- a/lib/web/plugs/set_locale_plug.ex
+++ b/lib/web/plugs/set_locale_plug.ex
@@ -11,8 +11,10 @@ defmodule Mobilizon.Web.Plugs.SetLocalePlug do
   import Plug.Conn, only: [assign: 3]
   alias Mobilizon.Web.Gettext, as: GettextBackend
 
+  @spec init(any()) :: nil
   def init(_), do: nil
 
+  @spec call(Plug.Conn.t(), any()) :: Plug.Conn.t()
   def call(conn, _) do
     locale =
       [
@@ -29,17 +31,22 @@ defmodule Mobilizon.Web.Plugs.SetLocalePlug do
     assign(conn, :locale, locale)
   end
 
+  @spec supported_locale?(String.t()) :: boolean()
   defp supported_locale?(locale) do
     GettextBackend
     |> Gettext.known_locales()
     |> Enum.member?(locale)
   end
 
+  @spec default_locale :: String.t()
   defp default_locale do
     Keyword.get(Mobilizon.Config.instance_config(), :default_language, "en")
   end
 
-  @spec determine_best_locale(String.t()) :: String.t()
+  @doc """
+  Determine the best available locale for a given locale ID
+  """
+  @spec determine_best_locale(String.t()) :: String.t() | nil
   def determine_best_locale(locale) when is_binary(locale) do
     locale = String.trim(locale)
     locales = Gettext.known_locales(GettextBackend)
@@ -58,5 +65,6 @@ defmodule Mobilizon.Web.Plugs.SetLocalePlug do
   def determine_best_locale(_), do: nil
 
   # Keep only the first part of the locale
+  @spec split_locale(String.t()) :: String.t()
   defp split_locale(locale), do: locale |> String.split("_", trim: true, parts: 2) |> hd
 end
diff --git a/lib/web/proxy/reverse_proxy.ex b/lib/web/proxy/reverse_proxy.ex
index 766dd5e06..9bb83b5a7 100644
--- a/lib/web/proxy/reverse_proxy.ex
+++ b/lib/web/proxy/reverse_proxy.ex
@@ -165,6 +165,11 @@ defmodule Mobilizon.Web.ReverseProxy do
     |> halt()
   end
 
+  @spec request(String.t(), String.t(), list(tuple()), Keyword.t()) ::
+          {:ok, 200 | 206 | 304, list(tuple()), any()}
+          | {:ok, 200 | 206 | 304, list(tuple())}
+          | {:error, {:invalid_http_response, pos_integer()}}
+          | {:error, any()}
   defp request(method, url, headers, hackney_opts) do
     Logger.debug("#{__MODULE__} #{method} #{url} #{inspect(headers)}")
     method = method |> String.downcase() |> String.to_existing_atom()
@@ -184,6 +189,8 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
+  @spec response(Plug.Conn.t(), any(), String.t(), pos_integer(), list(tuple()), Keyword.t()) ::
+          Plug.Conn.t()
   defp response(conn, client, url, status, headers, opts) do
     result =
       conn
@@ -209,18 +216,26 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
+  @spec chunk_reply(
+          Plug.Conn.t(),
+          any(),
+          Keyword.t(),
+          non_neg_integer(),
+          non_neg_integer() | :no_duration_limit
+        ) ::
+          {:ok, Plug.Conn.t()} | {:error, any(), Plug.Conn.t()}
   defp chunk_reply(conn, client, opts) do
     chunk_reply(conn, client, opts, 0, 0)
   end
 
   defp chunk_reply(conn, client, opts, sent_so_far, duration) do
-    with {:ok, duration} <-
+    with {:ok, {duration, now}} <-
            check_read_duration(
              duration,
              Keyword.get(opts, :max_read_duration, @max_read_duration)
            ),
          {:ok, data} <- @hackney.stream_body(client),
-         {:ok, duration} <- increase_read_duration(duration),
+         {:ok, duration} <- increase_read_duration({duration, now}),
          sent_so_far = sent_so_far + byte_size(data),
          :ok <- body_size_constraint(sent_so_far, Keyword.get(opts, :max_body_size)),
          {:ok, conn} <- chunk(conn, data) do
@@ -231,6 +246,8 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
+  @spec head_response(Plug.Conn.t(), any(), pos_integer(), list(tuple()), Keyword.t()) ::
+          Plug.Conn.t() | no_return()
   defp head_response(conn, _url, code, headers, opts) do
     conn
     |> put_resp_headers(build_resp_headers(headers, opts))
@@ -238,6 +255,8 @@ defmodule Mobilizon.Web.ReverseProxy do
   end
 
   # sobelow_skip ["XSS.SendResp"]
+  @spec error_or_redirect(Plug.Conn.t(), String.t(), pos_integer(), String.t(), Keyword.t()) ::
+          Plug.Conn.t()
   defp error_or_redirect(conn, url, code, body, opts) do
     if Keyword.get(opts, :redirect_on_failure, false) do
       conn
@@ -250,12 +269,14 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
+  @spec downcase_headers(list(tuple())) :: list(tuple())
   defp downcase_headers(headers) do
     Enum.map(headers, fn {k, v} ->
       {String.downcase(k), v}
     end)
   end
 
+  @spec get_content_type(list(tuple())) :: String.t()
   defp get_content_type(headers) do
     {_, content_type} =
       List.keyfind(headers, "content-type", 0, {"content-type", "application/octet-stream"})
@@ -264,12 +285,14 @@ defmodule Mobilizon.Web.ReverseProxy do
     content_type
   end
 
+  @spec put_resp_headers(Plug.Conn.t(), list(tuple())) :: Plug.Conn.t()
   defp put_resp_headers(conn, headers) do
     Enum.reduce(headers, conn, fn {k, v}, conn ->
       put_resp_header(conn, k, v)
     end)
   end
 
+  @spec build_req_headers(list(tuple()), Keyword.t()) :: list(tuple())
   defp build_req_headers(headers, opts) do
     headers
     |> downcase_headers()
@@ -290,6 +313,7 @@ defmodule Mobilizon.Web.ReverseProxy do
         end).()
   end
 
+  @spec build_resp_headers(list(tuple()), Keyword.t()) :: list(tuple())
   defp build_resp_headers(headers, opts) do
     headers
     |> Enum.filter(fn {k, _} -> k in @keep_resp_headers end)
@@ -298,6 +322,7 @@ defmodule Mobilizon.Web.ReverseProxy do
     |> (fn headers -> headers ++ Keyword.get(opts, :resp_headers, []) end).()
   end
 
+  @spec build_resp_cache_headers(list(tuple()), Keyword.t()) :: list(tuple())
   defp build_resp_cache_headers(headers, _opts) do
     has_cache? = Enum.any?(headers, fn {k, _} -> k in @resp_cache_headers end)
     has_cache_control? = List.keymember?(headers, "cache-control", 0)
@@ -321,6 +346,7 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
+  @spec build_resp_content_disposition_header(list(tuple()), Keyword.t()) :: list(tuple())
   defp build_resp_content_disposition_header(headers, opts) do
     opt = Keyword.get(opts, :inline_content_types, @inline_content_types)
 
@@ -359,6 +385,8 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
+  @spec header_length_constraint(list(tuple()), non_neg_integer()) ::
+          :ok | {:error, :body_too_large}
   defp header_length_constraint(headers, limit) when is_integer(limit) and limit > 0 do
     with {_, size} <- List.keyfind(headers, "content-length", 0),
          {size, _} <- Integer.parse(size),
@@ -375,15 +403,16 @@ defmodule Mobilizon.Web.ReverseProxy do
 
   defp header_length_constraint(_, _), do: :ok
 
+  @spec body_size_constraint(integer(), integer()) :: :ok | {:error, :body_too_large}
   defp body_size_constraint(size, limit) when is_integer(limit) and limit > 0 and size >= limit do
     {:error, :body_too_large}
   end
 
   defp body_size_constraint(_, _), do: :ok
 
-  @spec check_read_duration(any(), integer()) ::
+  @spec check_read_duration(any(), integer() | :no_duration_limit) ::
           {:ok, {integer(), integer()}}
-          | {:ok, :no_duration_limit, :no_duration_limit}
+          | {:ok, {:no_duration_limit, :no_duration_limit}}
           | {:error, :read_duration_exceeded}
   defp check_read_duration(duration, max)
        when is_integer(duration) and is_integer(max) and max > 0 do
@@ -394,8 +423,12 @@ defmodule Mobilizon.Web.ReverseProxy do
     end
   end
 
-  defp check_read_duration(_, _), do: {:ok, :no_duration_limit, :no_duration_limit}
+  defp check_read_duration(_, _), do: {:ok, {:no_duration_limit, :no_duration_limit}}
 
+  @spec increase_read_duration(
+          {previous_duration :: pos_integer | :no_duration_limit,
+           started :: pos_integer | :no_duration_limit}
+        ) :: {:ok, pos_integer()} | {:ok, :no_duration_limit}
   defp increase_read_duration({previous_duration, started})
        when is_integer(previous_duration) and is_integer(started) do
     duration = :erlang.system_time(:millisecond) - started
@@ -403,9 +436,10 @@ defmodule Mobilizon.Web.ReverseProxy do
   end
 
   defp increase_read_duration(_) do
-    {:ok, :no_duration_limit, :no_duration_limit}
+    {:ok, :no_duration_limit}
   end
 
+  @spec filename(String.t()) :: String.t() | nil
   def filename(url_or_path) do
     if path = URI.parse(url_or_path).path, do: Path.basename(path)
   end
diff --git a/lib/web/views/activity_pub/actor_view.ex b/lib/web/views/activity_pub/actor_view.ex
index eba9dd8a3..3e0f61930 100644
--- a/lib/web/views/activity_pub/actor_view.ex
+++ b/lib/web/views/activity_pub/actor_view.ex
@@ -17,6 +17,7 @@ defmodule Mobilizon.Web.ActivityPub.ActorView do
   @json_ld_header Utils.make_json_ld_header()
   @selected_member_roles ~w(creator administrator moderator member)a
 
+  @spec render(String.t(), map()) :: map()
   def render("actor.json", %{actor: actor}) do
     actor
     |> Convertible.model_to_as()
diff --git a/lib/web/views/activity_pub/object_view.ex b/lib/web/views/activity_pub/object_view.ex
index 9ababb1c3..a3ee04ec8 100644
--- a/lib/web/views/activity_pub/object_view.ex
+++ b/lib/web/views/activity_pub/object_view.ex
@@ -3,6 +3,7 @@ defmodule Mobilizon.Web.ActivityPub.ObjectView do
 
   alias Mobilizon.Federation.ActivityPub.{Activity, Utils}
 
+  @spec render(String.t(), map()) :: map()
   def render("activity.json", %{activity: %Activity{local: local, data: data} = activity}) do
     %{
       "id" => data["id"],
diff --git a/lib/web/views/auth_view.ex b/lib/web/views/auth_view.ex
index 67079bd8e..9ec29ff29 100644
--- a/lib/web/views/auth_view.ex
+++ b/lib/web/views/auth_view.ex
@@ -8,6 +8,7 @@ defmodule Mobilizon.Web.AuthView do
   alias Phoenix.HTML.Tag
   import Mobilizon.Web.Views.Utils
 
+  @spec render(String.t(), map()) :: String.t() | Plug.Conn.t()
   def render("callback.html", %{
         conn: conn,
         access_token: access_token,
diff --git a/lib/web/views/error_helpers.ex b/lib/web/views/error_helpers.ex
index 5a42c31c2..eb63a4d26 100644
--- a/lib/web/views/error_helpers.ex
+++ b/lib/web/views/error_helpers.ex
@@ -8,6 +8,7 @@ defmodule Mobilizon.Web.ErrorHelpers do
   @doc """
   Translates an error message using gettext.
   """
+  @spec translate_error({msg :: String.t(), opts :: map()}) :: String.t()
   def translate_error({msg, opts}) do
     # Because error messages were defined within Ecto, we must
     # call the Gettext module passing our Gettext backend. We
diff --git a/lib/web/views/error_view.ex b/lib/web/views/error_view.ex
index de8e7a704..28e8096e3 100644
--- a/lib/web/views/error_view.ex
+++ b/lib/web/views/error_view.ex
@@ -6,6 +6,7 @@ defmodule Mobilizon.Web.ErrorView do
   alias Mobilizon.Service.Metadata.Instance
   import Mobilizon.Web.Views.Utils
 
+  @spec render(String.t(), map()) :: map() | String.t() | Plug.Conn.t()
   def render("404.html", %{conn: conn}) do
     with tags <- Instance.build_tags(),
          {:ok, html} <- inject_tags(tags, get_locale(conn)) do
diff --git a/lib/web/views/json_ld/object_view.ex b/lib/web/views/json_ld/object_view.ex
index 333193a06..cc41e511b 100644
--- a/lib/web/views/json_ld/object_view.ex
+++ b/lib/web/views/json_ld/object_view.ex
@@ -8,6 +8,7 @@ defmodule Mobilizon.Web.JsonLD.ObjectView do
   alias Mobilizon.Web.Endpoint
   alias Mobilizon.Web.JsonLD.ObjectView
 
+  @spec render(String.t(), map()) :: map()
   def render("group.json", %{group: %Actor{} = group}) do
     %{
       "@context" => "http://schema.org",
@@ -93,6 +94,7 @@ defmodule Mobilizon.Web.JsonLD.ObjectView do
     }
   end
 
+  @spec render_location(map()) :: map() | nil
   defp render_location(%{physical_address: %Address{} = address}),
     do: render_one(address, ObjectView, "place.json", as: :address)
 
diff --git a/lib/web/views/page_view.ex b/lib/web/views/page_view.ex
index 3ce02182b..7c040bd9a 100644
--- a/lib/web/views/page_view.ex
+++ b/lib/web/views/page_view.ex
@@ -19,6 +19,8 @@ defmodule Mobilizon.Web.PageView do
   alias Mobilizon.Federation.ActivityStream.Convertible
   import Mobilizon.Web.Views.Utils
 
+  @doc false
+  @spec render(String.t(), %{conn: Plug.Conn.t()}) :: map() | String.t() | Plug.Conn.t()
   def render("actor.activity-json", %{conn: %{assigns: %{object: %Actor{} = actor}}}) do
     actor
     |> Convertible.model_to_as()
diff --git a/test/support/factory.ex b/test/support/factory.ex
index 953ac8c0b..4294ffcd7 100644
--- a/test/support/factory.ex
+++ b/test/support/factory.ex
@@ -11,6 +11,7 @@ defmodule Mobilizon.Factory do
   alias Mobilizon.Web.{Endpoint, Upload}
   alias Mobilizon.Web.Router.Helpers, as: Routes
 
+  @spec user_factory :: Mobilizon.Users.User.t()
   def user_factory do
     %Mobilizon.Users.User{
       password_hash: "Jane Smith",
@@ -23,6 +24,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec settings_factory :: Mobilizon.Users.Setting.t()
   def settings_factory do
     %Mobilizon.Users.Setting{
       timezone: nil,
@@ -37,6 +39,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec actor_factory :: Mobilizon.Actors.Actor.t()
   def actor_factory do
     preferred_username = sequence("thomas")
 
@@ -62,6 +65,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec group_factory :: Mobilizon.Actors.Actor.t()
   def group_factory do
     preferred_username = sequence("myGroup")
 
@@ -82,6 +86,7 @@ defmodule Mobilizon.Factory do
     )
   end
 
+  @spec instance_actor_factory :: Mobilizon.Actors.Actor.t()
   def instance_actor_factory do
     preferred_username = "relay"
     domain = "#{sequence("mydomain")}.com"
@@ -104,6 +109,7 @@ defmodule Mobilizon.Factory do
     )
   end
 
+  @spec follower_factory :: Mobilizon.Actors.Follower.t()
   def follower_factory do
     uuid = Ecto.UUID.generate()
 
@@ -116,6 +122,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec tag_factory :: Mobilizon.Events.Tag.t()
   def tag_factory do
     %Mobilizon.Events.Tag{
       title: sequence("MyTag"),
@@ -123,6 +130,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec tag_relation_factory :: Mobilizon.Events.TagRelation.t()
   def tag_relation_factory do
     %Mobilizon.Events.TagRelation{
       tag: build(:tag),
@@ -130,6 +138,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec address_factory :: Mobilizon.Addresses.Address.t()
   def address_factory do
     %Mobilizon.Addresses.Address{
       description: sequence("MyAddress"),
@@ -143,6 +152,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec comment_factory :: Mobilizon.Discussions.Comment.t()
   def comment_factory do
     uuid = Ecto.UUID.generate()
 
@@ -165,6 +175,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec event_factory :: Mobilizon.Events.Event.t()
   def event_factory do
     actor = build(:actor)
     start = Timex.shift(DateTime.utc_now(), hours: 2)
@@ -198,6 +209,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec participant_factory :: Mobilizon.Events.Participant.t()
   def participant_factory do
     uuid = Ecto.UUID.generate()
 
@@ -214,6 +226,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec session_factory :: Mobilizon.Events.Session.t()
   def session_factory do
     %Mobilizon.Events.Session{
       title: sequence("MySession"),
@@ -222,6 +235,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec track_factory :: Mobilizon.Events.Track.t()
   def track_factory do
     %Mobilizon.Events.Track{
       name: sequence("MyTrack"),
@@ -229,6 +243,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec bot_factory :: Mobilizon.Actors.Bot.t()
   def bot_factory do
     %Mobilizon.Actors.Bot{
       source: "https://mysource.tld/feed.ics",
@@ -238,6 +253,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec member_factory :: Mobilizon.Actors.Member.t()
   def member_factory do
     uuid = Ecto.UUID.generate()
 
@@ -250,6 +266,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec feed_token_factory :: Mobilizon.Events.FeedToken.t()
   def feed_token_factory do
     user = build(:user)
 
@@ -260,6 +277,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec file_factory :: Mobilizon.Medias.File.t()
   def file_factory do
     File.cp!("test/fixtures/image.jpg", "test/fixtures/image_tmp.jpg")
 
@@ -285,6 +303,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec media_factory :: Mobilizon.Medias.Media.t()
   def media_factory do
     %Mobilizon.Medias.Media{
       file: build(:file),
@@ -292,6 +311,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec report_factory :: Mobilizon.Reports.Report.t()
   def report_factory do
     %Mobilizon.Reports.Report{
       content: "This is problematic",
@@ -304,6 +324,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec report_note_factory :: Mobilizon.Reports.Note.t()
   def report_note_factory do
     %Mobilizon.Reports.Note{
       content: "My opinion",
@@ -312,6 +333,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec todo_list_factory :: Mobilizon.Todos.TodoList.t()
   def todo_list_factory do
     uuid = Ecto.UUID.generate()
 
@@ -324,6 +346,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec todo_factory :: Mobilizon.Todos.Todo.t()
   def todo_factory do
     uuid = Ecto.UUID.generate()
 
@@ -340,6 +363,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec resource_factory :: Mobilizon.Resources.Resource.t()
   def resource_factory do
     uuid = Ecto.UUID.generate()
     title = sequence("my resource")
@@ -358,6 +382,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec admin_setting_factory :: Mobilizon.Admin.Setting.t()
   def admin_setting_factory do
     %Mobilizon.Admin.Setting{
       group: sequence("group"),
@@ -366,6 +391,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec post_factory :: Mobilizon.Posts.Post.t()
   def post_factory do
     uuid = Ecto.UUID.generate()
 
@@ -386,6 +412,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec tombstone_factory :: Mobilizon.Tombstone.t()
   def tombstone_factory do
     uuid = Ecto.UUID.generate()
 
@@ -395,6 +422,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec discussion_factory :: Mobilizon.Discussions.Discussion.t()
   def discussion_factory do
     uuid = Ecto.UUID.generate()
     actor = build(:actor)
@@ -413,6 +441,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec mobilizon_activity_factory :: Mobilizon.Activities.Activity.t()
   def mobilizon_activity_factory do
     group = build(:group)
     actor = build(:actor)
@@ -433,6 +462,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec mobilizon_activity_setting_factory :: Mobilizon.Users.ActivitySetting.t()
   def mobilizon_activity_setting_factory do
     %Mobilizon.Users.ActivitySetting{
       key: "event_created",
@@ -442,6 +472,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec push_subscription_factory :: Mobilizon.Users.PushSubscription.t()
   def push_subscription_factory do
     %Mobilizon.Users.PushSubscription{
       digest: "",
@@ -452,6 +483,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec share_factory :: Mobilizon.Share.t()
   def share_factory do
     %Mobilizon.Share{
       actor: build(:actor),
@@ -460,6 +492,7 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  @spec event_metadata_factory :: Mobilizon.Events.EventMetadata.t()
   def event_metadata_factory do
     %Mobilizon.Events.EventMetadata{
       key: sequence("mz:custom:something"),