diff --git a/test/service/metadata/instance_test.exs b/test/service/metadata/instance_test.exs
new file mode 100644
index 000000000..8e7033e80
--- /dev/null
+++ b/test/service/metadata/instance_test.exs
@@ -0,0 +1,24 @@
+defmodule Mobilizon.Service.Metadata.InstanceTest do
+  alias Mobilizon.Config
+  alias Mobilizon.Service.Metadata.{Instance, Utils}
+  alias Mobilizon.Web.Endpoint
+  use Mobilizon.DataCase
+
+  describe "build_tags/0 for the instance" do
+    test "gives tags" do
+      title = "#{Config.instance_name()} - Mobilizon"
+      description = Utils.process_description(Config.instance_description())
+
+      assert Instance.build_tags() |> Utils.stringify_tags() ==
+               "<title>#{title}</title><meta content=\"#{description}\" name=\"description\"><meta content=\"#{
+                 title
+               }\" property=\"og:title\"><meta content=\"#{Endpoint.url()}\" property=\"og:url\"><meta content=\"#{
+                 description
+               }\" property=\"og:description\"><meta content=\"website\" property=\"og:type\"><script type=\"application/ld+json\">{\n\"@context\": \"http://schema.org\",\n\"@type\": \"WebSite\",\n\"name\": \"#{
+                 title
+               }\",\n\"url\": \"#{Endpoint.url()}\",\n\"potentialAction\": {\n\"@type\": \"SearchAction\",\n\"target\": \"#{
+                 Endpoint.url()
+               }/search?term={search_term}\",\n\"query-input\": \"required name=search_term\"\n}\n}</script>\n"
+    end
+  end
+end
diff --git a/test/service/metadata/metadata_test.exs b/test/service/metadata/metadata_test.exs
new file mode 100644
index 000000000..478d2f0a5
--- /dev/null
+++ b/test/service/metadata/metadata_test.exs
@@ -0,0 +1,143 @@
+defmodule Mobilizon.Service.MetadataTest do
+  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Discussions.Comment
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Posts.Post
+  alias Mobilizon.Service.Metadata
+  alias Mobilizon.Tombstone
+  use Mobilizon.DataCase
+  import Mobilizon.Factory
+
+  describe "build_tags/2 for an actor" do
+    test "that is a group gives tags" do
+      %Actor{} = group = insert(:group, name: "My group")
+
+      assert group |> Metadata.build_tags() |> Metadata.Utils.stringify_tags() ==
+               "<meta content=\"#{group.name} (@#{group.preferred_username})\" property=\"og:title\"><meta content=\"#{
+                 group.url
+               }\" property=\"og:url\"><meta content=\"The event organizer didn&#39;t add any description.\" property=\"og:description\"><meta content=\"profile\" property=\"og:type\"><meta content=\"#{
+                 group.preferred_username
+               }\" property=\"profile:username\"><meta content=\"summary\" property=\"twitter:card\"><meta content=\"#{
+                 group.avatar.url
+               }\" property=\"og:image\"><script type=\"application/ld+json\">{\"@context\":\"http://schema.org\",\"@type\":\"Organization\",\"address\":null,\"name\":\"#{
+                 group.name
+               }\",\"url\":\"#{group.url}\"}</script>"
+
+      assert group
+             |> Map.put(:avatar, nil)
+             |> Metadata.build_tags()
+             |> Metadata.Utils.stringify_tags() ==
+               "<meta content=\"#{group.name} (@#{group.preferred_username})\" property=\"og:title\"><meta content=\"#{
+                 group.url
+               }\" property=\"og:url\"><meta content=\"The event organizer didn&#39;t add any description.\" property=\"og:description\"><meta content=\"profile\" property=\"og:type\"><meta content=\"#{
+                 group.preferred_username
+               }\" property=\"profile:username\"><meta content=\"summary\" property=\"twitter:card\"><script type=\"application/ld+json\">{\"@context\":\"http://schema.org\",\"@type\":\"Organization\",\"address\":null,\"name\":\"#{
+                 group.name
+               }\",\"url\":\"#{group.url}\"}</script>"
+    end
+
+    test "that is not a group doesn't give anything" do
+      %Actor{} = person = insert(:actor)
+
+      assert person |> Metadata.build_tags() |> Metadata.Utils.stringify_tags() == ""
+      assert person |> Metadata.build_tags("fr") |> Metadata.Utils.stringify_tags() == ""
+    end
+  end
+
+  describe "build_tags/2 for an event" do
+    test "gives tags" do
+      alias Mobilizon.Web.Endpoint
+
+      %Event{} = event = insert(:event)
+
+      # Because the description in Schema.org data is double-escaped
+      a = "\n"
+      b = "\\n"
+
+      assert event
+             |> Metadata.build_tags()
+             |> Metadata.Utils.stringify_tags() ==
+               "<title>#{event.title} - Mobilizon</title><meta content=\"#{event.description}\" name=\"description\"><meta content=\"#{
+                 event.title
+               }\" property=\"og:title\"><meta content=\"#{event.url}\" property=\"og:url\"><meta content=\"#{
+                 event.description
+               }\" property=\"og:description\"><meta content=\"website\" property=\"og:type\"><link href=\"#{
+                 event.url
+               }\" rel=\"canonical\"><meta content=\"#{event.picture.file.url}\" property=\"og:image\"><meta content=\"summary_large_image\" property=\"twitter:card\"><script type=\"application/ld+json\">{\"@context\":\"https://schema.org\",\"@type\":\"Event\",\"description\":\"#{
+                 String.replace(event.description, a, b)
+               }\",\"endDate\":\"#{DateTime.to_iso8601(event.ends_on)}\",\"eventStatus\":\"https://schema.org/EventScheduled\",\"image\":[\"#{
+                 event.picture.file.url
+               }\"],\"location\":{\"@type\":\"Place\",\"address\":{\"@type\":\"PostalAddress\",\"addressCountry\":\"My Country\",\"addressLocality\":\"My Locality\",\"addressRegion\":\"My Region\",\"postalCode\":\"My Postal Code\",\"streetAddress\":\"My Street Address\"},\"name\":\"#{
+                 event.physical_address.description
+               }\"},\"name\":\"#{event.title}\",\"organizer\":{\"@type\":\"Person\",\"name\":\"#{
+                 event.organizer_actor.preferred_username
+               }\"},\"performer\":{\"@type\":\"Person\",\"name\":\"#{
+                 event.organizer_actor.preferred_username
+               }\"},\"startDate\":\"#{DateTime.to_iso8601(event.begins_on)}\"}</script>"
+
+      assert event
+             |> Map.put(:picture, nil)
+             |> Metadata.build_tags()
+             |> Metadata.Utils.stringify_tags() ==
+               "<title>#{event.title} - Mobilizon</title><meta content=\"#{event.description}\" name=\"description\"><meta content=\"#{
+                 event.title
+               }\" property=\"og:title\"><meta content=\"#{event.url}\" property=\"og:url\"><meta content=\"#{
+                 event.description
+               }\" property=\"og:description\"><meta content=\"website\" property=\"og:type\"><link href=\"#{
+                 event.url
+               }\" rel=\"canonical\"><meta content=\"summary_large_image\" property=\"twitter:card\"><script type=\"application/ld+json\">{\"@context\":\"https://schema.org\",\"@type\":\"Event\",\"description\":\"#{
+                 String.replace(event.description, a, b)
+               }\",\"endDate\":\"#{DateTime.to_iso8601(event.ends_on)}\",\"eventStatus\":\"https://schema.org/EventScheduled\",\"image\":[\"#{
+                 "#{Endpoint.url()}/img/mobilizon_default_card.png"
+               }\"],\"location\":{\"@type\":\"Place\",\"address\":{\"@type\":\"PostalAddress\",\"addressCountry\":\"My Country\",\"addressLocality\":\"My Locality\",\"addressRegion\":\"My Region\",\"postalCode\":\"My Postal Code\",\"streetAddress\":\"My Street Address\"},\"name\":\"#{
+                 event.physical_address.description
+               }\"},\"name\":\"#{event.title}\",\"organizer\":{\"@type\":\"Person\",\"name\":\"#{
+                 event.organizer_actor.preferred_username
+               }\"},\"performer\":{\"@type\":\"Person\",\"name\":\"#{
+                 event.organizer_actor.preferred_username
+               }\"},\"startDate\":\"#{DateTime.to_iso8601(event.begins_on)}\"}</script>"
+    end
+  end
+
+  describe "build_tags/2 for a post" do
+    test "gives tags" do
+      %Post{} = post = insert(:post)
+
+      assert post
+             |> Metadata.build_tags()
+             |> Metadata.Utils.stringify_tags() ==
+               "<meta content=\"#{post.title}\" property=\"og:title\"><meta content=\"#{post.url}\" property=\"og:url\"><meta content=\"#{
+                 Metadata.Utils.process_description(post.body)
+               }\" property=\"og:description\"><meta content=\"article\" property=\"og:type\"><meta content=\"summary\" property=\"twitter:card\"><link href=\"#{
+                 post.url
+               }\" rel=\"canonical\"><meta content=\"summary_large_image\" property=\"twitter:card\"><script type=\"application/ld+json\">{\"@context\":\"https://schema.org\",\"@type\":\"Article\",\"author\":{\"@type\":\"Organization\",\"name\":\"#{
+                 post.attributed_to.preferred_username
+               }\"},\"dateModified\":\"#{DateTime.to_iso8601(post.updated_at)}\",\"datePublished\":\"#{
+                 DateTime.to_iso8601(post.publish_at)
+               }\",\"name\":\"My Awesome article\"}</script>"
+    end
+  end
+
+  describe "build_tags/2 for a comment" do
+    test "gives tags" do
+      %Comment{} = comment = insert(:comment)
+
+      assert comment
+             |> Metadata.build_tags()
+             |> Metadata.Utils.stringify_tags() ==
+               "<meta content=\"#{comment.actor.preferred_username}\" property=\"og:title\"><meta content=\"#{
+                 comment.url
+               }\" property=\"og:url\"><meta content=\"#{comment.text}\" property=\"og:description\"><meta content=\"website\" property=\"og:type\"><meta content=\"summary\" property=\"twitter:card\">"
+    end
+  end
+
+  describe "build_tags/2 for a tombstone" do
+    test "gives nothing" do
+      %Tombstone{} = tombstone = insert(:tombstone)
+
+      assert tombstone
+             |> Metadata.build_tags()
+             |> Metadata.Utils.stringify_tags() == ""
+    end
+  end
+end
diff --git a/test/service/metadata/utils_test.exs b/test/service/metadata/utils_test.exs
new file mode 100644
index 000000000..9ba6742ae
--- /dev/null
+++ b/test/service/metadata/utils_test.exs
@@ -0,0 +1,60 @@
+defmodule Mobilizon.Service.Metadata.UtilsTest do
+  alias Mobilizon.Service.Metadata.Utils
+  use Mobilizon.DataCase
+
+  describe "process_description/3" do
+    test "process_description/3 strip tags" do
+      assert Utils.process_description("<p>This is my biography</p>") == "This is my biography"
+    end
+
+    test "process_description/3 cuts after a limit" do
+      assert Utils.process_description("<p>This is my biography</p>", "fr", 10) ==
+               "This is my…"
+    end
+
+    test "process_description/3 cuts after the default limit" do
+      assert Utils.process_description(
+               "<h1>Biography</h1><p>It all started when someone wanted a <b>very long string</b> to be cut. However it's difficult to invent things to write when you've got nothing to say. Anyway, what's the deal here. We just need to reach 200 characters.",
+               "fr"
+             ) ==
+               "Biography It all started when someone wanted a very long string to be cut. However it&#39;s difficult to invent things to write when you&#39;ve got nothing to say. Anyway, what&#39;s the deal here. We…"
+    end
+
+    test "process_description/3 returns default if no description is provided" do
+      assert Utils.process_description(nil) ==
+               "The event organizer didn't add any description."
+
+      assert Utils.process_description("", "en") ==
+               "The event organizer didn't add any description."
+    end
+  end
+
+  describe "default_description/1" do
+    test "returns default description with a correct locale" do
+      assert Utils.default_description("en") == "The event organizer didn't add any description."
+    end
+
+    test "returns default description with no locale provided" do
+      assert Utils.default_description() == "The event organizer didn't add any description."
+    end
+  end
+
+  describe "stringify_tags/1" do
+    test "converts tags to string" do
+      alias Phoenix.HTML.Tag
+
+      tag_1 = Tag.tag(:meta, property: "og:url", content: "one")
+      tag_2 = "<meta content=\"two\" property=\"og:url\">"
+      tag_3 = Tag.tag(:meta, property: "og:url", content: "three")
+
+      assert Utils.stringify_tags([tag_1, tag_2, tag_3]) ==
+               "<meta content=\"one\" property=\"og:url\"><meta content=\"two\" property=\"og:url\"><meta content=\"three\" property=\"og:url\">"
+    end
+  end
+
+  describe "strip_tags/1" do
+    test "removes tags from string" do
+      assert Utils.strip_tags("<h1>Hello</h1><p>How are you</p>") == "Hello How are you"
+    end
+  end
+end