Index: src/builtin.c
==================================================================
--- src/builtin.c
+++ src/builtin.c
@@ -704,10 +704,11 @@
   /* This list ordering isn't strictly important. */
   {"confirmer",      0, 0},
   {"copybutton",     0, "dom\0"},
   {"dom",            0, 0},
   {"fetch",          0, 0},
+  {"info-diff",      0, "dom\0"},
   {"numbered-lines", 0, "popupwidget\0copybutton\0"},
   {"pikchr",         0, "dom\0"},
   {"popupwidget",    0, "dom\0"},
   {"storage",        0, 0},
   {"tabs",           0, "dom\0"}

Index: src/default.css
==================================================================
--- src/default.css
+++ src/default.css
@@ -1763,10 +1763,13 @@
 body.chat #chat-drop-details img {
   max-width: 45%;
   max-height: 45%;
 }
 
+input[type="checkbox"].diff-toggle {
+  float: right;
+}
 /* Objects in the "desktoponly" class are invisible on mobile */
 @media screen and (max-width: 600px) {
   .desktoponly {
     display: none;
   }

ADDED   src/fossil.info-diff.js
Index: src/fossil.info-diff.js
==================================================================
--- /dev/null
+++ src/fossil.info-diff.js
@@ -0,0 +1,14 @@
+"use strict";
+window.fossil.onPageLoad(function(){
+  const F = window.fossil, D = F.dom;
+  const addToggle = function(diffElem){
+    const sib = diffElem.previousElementSibling,
+          btn = sib ? D.addClass(D.checkbox(true), 'diff-toggle') : 0;
+    if(!sib) return;
+    D.append(sib,btn);
+    btn.addEventListener('click', function(){
+      diffElem.classList.toggle('hidden');
+    }, false);
+  };
+  document.querySelectorAll('pre.udiff, table.sbsdiffcols').forEach(addToggle);
+});

Index: src/info.c
==================================================================
--- src/info.c
+++ src/info.c
@@ -940,10 +940,11 @@
     append_file_change_line(zUuid, zName, zOld, zNew, zOldName, 
                             diffFlags,pRe,mperm);
   }
   db_finalize(&q3);
   append_diff_javascript(diffType==2);
+  builtin_fossil_js_bundle_or("info-diff",NULL);
   cookie_render();
   style_finish_page();
 }
 
 /*

Index: src/main.mk
==================================================================
--- src/main.mk
+++ src/main.mk
@@ -225,10 +225,11 @@
   $(SRCDIR)/fossil.bootstrap.js \
   $(SRCDIR)/fossil.confirmer.js \
   $(SRCDIR)/fossil.copybutton.js \
   $(SRCDIR)/fossil.dom.js \
   $(SRCDIR)/fossil.fetch.js \
+  $(SRCDIR)/fossil.info-diff.js \
   $(SRCDIR)/fossil.numbered-lines.js \
   $(SRCDIR)/fossil.page.fileedit.js \
   $(SRCDIR)/fossil.page.forumpost.js \
   $(SRCDIR)/fossil.page.pikchrshow.js \
   $(SRCDIR)/fossil.page.wikiedit.js \

Index: win/Makefile.mingw
==================================================================
--- win/Makefile.mingw
+++ win/Makefile.mingw
@@ -634,10 +634,11 @@
   $(SRCDIR)/fossil.bootstrap.js \
   $(SRCDIR)/fossil.confirmer.js \
   $(SRCDIR)/fossil.copybutton.js \
   $(SRCDIR)/fossil.dom.js \
   $(SRCDIR)/fossil.fetch.js \
+  $(SRCDIR)/fossil.info-diff.js \
   $(SRCDIR)/fossil.numbered-lines.js \
   $(SRCDIR)/fossil.page.fileedit.js \
   $(SRCDIR)/fossil.page.forumpost.js \
   $(SRCDIR)/fossil.page.pikchrshow.js \
   $(SRCDIR)/fossil.page.wikiedit.js \

Index: win/Makefile.msc
==================================================================
--- win/Makefile.msc
+++ win/Makefile.msc
@@ -559,10 +559,11 @@
         "$(SRCDIR)\fossil.bootstrap.js" \
         "$(SRCDIR)\fossil.confirmer.js" \
         "$(SRCDIR)\fossil.copybutton.js" \
         "$(SRCDIR)\fossil.dom.js" \
         "$(SRCDIR)\fossil.fetch.js" \
+        "$(SRCDIR)\fossil.info-diff.js" \
         "$(SRCDIR)\fossil.numbered-lines.js" \
         "$(SRCDIR)\fossil.page.fileedit.js" \
         "$(SRCDIR)\fossil.page.forumpost.js" \
         "$(SRCDIR)\fossil.page.pikchrshow.js" \
         "$(SRCDIR)\fossil.page.wikiedit.js" \
@@ -1164,10 +1165,11 @@
 	echo "$(SRCDIR)\fossil.bootstrap.js" >> $@
 	echo "$(SRCDIR)\fossil.confirmer.js" >> $@
 	echo "$(SRCDIR)\fossil.copybutton.js" >> $@
 	echo "$(SRCDIR)\fossil.dom.js" >> $@
 	echo "$(SRCDIR)\fossil.fetch.js" >> $@
+	echo "$(SRCDIR)\fossil.info-diff.js" >> $@
 	echo "$(SRCDIR)\fossil.numbered-lines.js" >> $@
 	echo "$(SRCDIR)\fossil.page.fileedit.js" >> $@
 	echo "$(SRCDIR)\fossil.page.forumpost.js" >> $@
 	echo "$(SRCDIR)\fossil.page.pikchrshow.js" >> $@
 	echo "$(SRCDIR)\fossil.page.wikiedit.js" >> $@