diff --git a/app/controllers/concerns/web_app_controller_concern.rb b/app/controllers/concerns/web_app_controller_concern.rb
index 39fc948e909..5a540d17b44 100644
--- a/app/controllers/concerns/web_app_controller_concern.rb
+++ b/app/controllers/concerns/web_app_controller_concern.rb
@@ -6,6 +6,7 @@ module WebAppControllerConcern
   included do
     vary_by 'Accept, Accept-Language, Cookie'
 
+    before_action :adjust_format_for_zip_tlds
     before_action :redirect_unauthenticated_to_permalinks!
     before_action :set_referer_header
     before_action :redirect_to_tos_interstitial!
@@ -46,6 +47,14 @@ module WebAppControllerConcern
 
   protected
 
+  # This endpoint will never serve zip files, but may serve paths ending with `.zip` due to the `.zip` TLD.
+  # When that happens from a browser, Rails will unfortunately determine the requested format to be `:zip`
+  # instead of `:html`, so override this.
+  # We don't just override `format` in all cases, because we want to handle `:json` as well.
+  def adjust_format_for_zip_tlds
+    request.format = :html if request.format == :zip
+  end
+
   def redirect_to_tos_interstitial!
     return unless current_user&.require_tos_interstitial?