diff --git a/src/html_renderer.ml b/src/html_renderer.ml
index d493b42..29e10ee 100644
--- a/src/html_renderer.ml
+++ b/src/html_renderer.ml
@@ -3,6 +3,22 @@
     Renders the output of computations on a given program as an HTML webpage.
  *)
 
+(** Generates a fresh unique identifier *)
+let fresh_uuid =
+  let next = ref 0 in
+  fun () ->
+    let out = !next in
+    incr next ; out
+
+(** Checks whether a submethod is relevant to show, or whether it should be
+    hidden by default. *)
+let is_sub_relevant sub = Renderer.AnnotAsm.(
+  List.exists
+    (fun instr -> instr.instr_annot.Renderer.events <> [])
+    sub.sub_asm
+)
+
+
 (** Box `AnnotAsm.asm_info_t` as a Jingoo tvalue *)
 let render_prog_box annotated_prog = Jingoo.Jg_types.(Renderer.AnnotAsm.(
     let render_addr addr = (Format.sprintf "%04x" addr) in
@@ -11,6 +27,10 @@ let render_prog_box annotated_prog = Jingoo.Jg_types.(Renderer.AnnotAsm.(
           ("sub_section", box_string render_sub.sub_section);
           ("sub_name", box_string render_sub.sub_name);
           ("sub_addr", box_string (Format.sprintf "%016x" render_sub.sub_addr));
+          ("sub_uuid", box_int @@ fresh_uuid ());
+          ("sub_relevant", box_int @@ (match is_sub_relevant render_sub with
+               | true -> 1
+               | false -> 0));
           ("sub_asm", List.map (fun row -> [
               ("instr_addr", box_string (render_addr row.instr_addr));
               ("instr_bytes", box_string (
diff --git a/src/render_html.jingoo b/src/render_html.jingoo
index f63dc5d..4c46acc 100644
--- a/src/render_html.jingoo
+++ b/src/render_html.jingoo
@@ -28,6 +28,17 @@
       .subroutine {
         margin: 20px 0;
       }
+
+      .sub_collapser {
+        background-color: #8c8c8c;
+        color: white;
+        font-weight: bold;
+        border-radius: 50%;
+        text-align: center;
+        display: inline-block;
+        width: 1em;
+      }
+
       .sub_body {
         margin-left: 4ex;
       }
@@ -70,6 +81,22 @@
 				}
       }
     </script>
+
+    <script>
+      function toggle_visibility(id) {
+         var e = document.getElementById(id);
+         var label = document.getElementById(id + "_collapser");
+
+         if(e.style.display == 'none') {
+            label.innerHTML = label.innerHTML.replace("+","-");
+            e.style.display = 'block';
+          }
+         else {
+            label.innerHTML = label.innerHTML.replace("-","+");
+            e.style.display = 'none';
+         }
+      }
+    </script>
   </head>
 	<body>
     <div class="prog_container">
@@ -79,11 +106,17 @@
       {% for subroutine in prog.prog %}
       <div class="subroutine">
         <div class="sub_headline">
+          <span class="sub_collapser"
+                id="sub_body_{{subroutine.sub_uuid}}_collapser"
+                onclick="toggle_visibility('sub_body_{{ subroutine.sub_uuid }}')"
+                >
+            -
+          </span>
           <span class="addr">{{ subroutine.sub_addr }}</span>
           <span class="sub_section">[{{ subroutine.sub_section }}]</span>
           <span class="sub_name">&lt;{{ subroutine.sub_name }}&gt;</span>:
         </div>
-        <div class="sub_body">
+        <div class="sub_body" id="sub_body_{{ subroutine.sub_uuid }}">
           {% for row in subroutine.sub_asm %}
           {% for event in row.instr_events %}
             {% if event.typ == "start" %}
@@ -106,6 +139,9 @@
           {% endfor %}
         </div>
       </div>
+      {% if not subroutine.sub_relevant %}
+      <script>toggle_visibility('sub_body_{{ subroutine.sub_uuid }}');</script>
+      {% endif %}
       {% endfor %}
     </div>
     {% endfor %}
