do not preload captions

assets/js/player.js

@@ -21,6 +21,7 @@ var options = {
         ]
     },
     html5: {
+        preloadTextTracks: false,
         hls: {
             overrideNative: true
         }
@@ -547,3 +548,10 @@ window.addEventListener('keydown', e => {
 if (player.share) {
     player.share(shareOptions);
 }
+
+// show the preferred caption by default
+if (player_data.preferred_caption_found) {
+    player.ready(() => {
+        player.textTracks()[1].mode = 'showing';
+    });
+}

src/invidious/views/components/player.ecr

@@ -24,9 +24,9 @@
             <% end %>
         <% end %>
 
-        <% preferred_captions.each_with_index do |caption, i| %>
+        <% preferred_captions.each do |caption| %>
             <track kind="captions" src="/api/v1/captions/<%= video.id %>?label=<%= caption.name.simpleText %>&hl=<%= env.get("preferences").as(Preferences).locale %>"
-                label="<%= caption.name.simpleText %>" <% if i == 0 %>default<% end %>>
+                label="<%= caption.name.simpleText %>">
         <% end %>
 
         <% captions.each do |caption| %>
@@ -42,7 +42,8 @@
     "aspect_ratio" => aspect_ratio,
     "title" => video.title,
     "description" => HTML.escape(video.short_description),
-    "thumbnail" => thumbnail
+    "thumbnail" => thumbnail,
+    "preferred_caption_found" => !preferred_captions.empty?
 }.to_pretty_json
 %>
 </script>