diff --git a/README.md b/README.md
index b98afd2f7..22a12bd5b 100644
--- a/README.md
+++ b/README.md
@@ -291,7 +291,7 @@ version of what's in `apps.json`:
         sendCustomizedApp({
           id : "7chname",
           storage:[
-            {name:"7chname.app.js", content:app_source_code},
+            {name:"7chname.app.js", url:"app.js", content:app_source_code},
             {name:"7chname.img", content:'require("heatshrink").decompress(atob("mEwg...4"))', evaluate:true},
           ]
         });
@@ -304,6 +304,10 @@ version of what's in `apps.json`:
 This'll then be loaded in to the watch. See [apps/qrcode/grcode.html](the QR Code app)
 for a clean example.
 
+**Note:** we specify a `url` for JS files even though it doesn't have to exist
+and will never be loaded. This is so the app loader can tell if it's a JavaScript
+file based on the extension, and if so it can minify and pretokenise it.
+
 ### `apps.json`: `interface` element
 
 Apps that create data that can be read back can define a `interface` element in `apps.json`,
diff --git a/apps/beer/custom.html b/apps/beer/custom.html
index c4a9a3511..a357ab378 100644
--- a/apps/beer/custom.html
+++ b/apps/beer/custom.html
@@ -199,7 +199,7 @@ g.clear();`;
 
         sendCustomizedApp({
           storage:[
-            {name:"beer.app.js", content:app}
+            {name:"beer.app.js", url:"app.js", content:app}
           ]
         });
       });
diff --git a/apps/espruinoctrl/custom.html b/apps/espruinoctrl/custom.html
index 007f3a123..f8e7e38b9 100644
--- a/apps/espruinoctrl/custom.html
+++ b/apps/espruinoctrl/custom.html
@@ -266,7 +266,7 @@ function sendCommand(device, text, callback) {
 `;
         sendCustomizedApp({
           storage:[
-            {name:"espruinoctrl.app.js", content:app},
+            {name:"espruinoctrl.app.js", url:"app.js", content:app},
           ]
         });
       });
diff --git a/apps/grocery/grocery.html b/apps/grocery/grocery.html
index 9222dd20c..14c406d75 100644
--- a/apps/grocery/grocery.html
+++ b/apps/grocery/grocery.html
@@ -14,7 +14,7 @@
         </tr>
       </thead>
       <tbody id="products">
-        
+
       </tbody>
     </table>
     <br><br>
@@ -34,7 +34,7 @@
     </form>
     <br><br>
     <button id="reset" class="btn btn-error">Reset</button> <button id="upload" class="btn btn-primary">Upload</button>
-    
+
     <script src="../../core/lib/customize.js"></script>
 
     <script>
@@ -53,15 +53,15 @@
       var $reset = document.getElementById('reset')
 
       renderProducts()
-      
+
       $reset.addEventListener('click', reset)
 
       $form.addEventListener('submit', event => {
         event.preventDefault()
-        
+
         var name = $name.value.trim()
         if(!name) return;
-        
+
         var quantity = parseInt($quantity.value)
 
         products.push({
@@ -95,13 +95,13 @@
         $list.innerHTML = ''
         products.forEach((product,index) => {
           var $product = document.createElement('tr')
-          
+
           $product.innerHTML = `<td>${product.name}</td><td>${product.quantity}</td><td><button class="btn btn-error" onclick="removeProduct(${index})">remove</button></td>`
           $list.appendChild($product)
         })
 
         $name.focus()
-        
+
       }
 
       document.getElementById("upload").addEventListener("click", function() {
@@ -152,7 +152,7 @@ E.showMenu(mainMenu);
         var icon = `require("heatshrink").decompress(atob("mEwxH+AH4A/AH4AQ0QACF1nGAAIxpFoYwqFwwwnRggwGB4eFAggACLzwHCMAeF1WGAgOGw2x2IGCLzYGEF4YpBwotCFwJfWFwo1GSAYtBAIIABRq4vFMhAwBzoAFdzIuKAAOc4IAGGC4qEMZOiF44wXFxovleBYvIGCwmB0WjE4V/AgfG1IvCzujFQOjwoECF6WFwovBDYOFEwN/AgIwCAgOFBwYrBBAQEBzodCF6AAHww1CBpIODAAYvRDAWG2IEBAYYJFBxICCF6Ox1WxAAQfBAYQlCAAIOJAQIvUADQvn1WGR4RfbP4gAFBwgFCF7a5EdwQADF46/cL9wAQF94AGF85bB1TvmF47vdJ4bvFF8qPRFgLv/L7jPCaQq/fYYrvgJgoAGd/7v/F/4v/F5oAdF54weFyAA/AH4A3A="))`;
         sendCustomizedApp({
           storage:[
-            {name:"grocery.app.js", content:app},
+            {name:"grocery.app.js", url:"app.js", content:app},
             {name:"grocery.img", content:icon, evaluate:true},
             {name:"grocery"}
           ]
diff --git a/apps/locale/locale.html b/apps/locale/locale.html
index bf3770e99..2389203bb 100644
--- a/apps/locale/locale.html
+++ b/apps/locale/locale.html
@@ -210,7 +210,7 @@ exports = {
         console.log("Locale Module is:",localeModule);
         sendCustomizedApp({
           storage:[
-            {name:"locale", content:localeModule}
+            {name:"locale", url:"locale.js", content:localeModule}
           ]
         });
       });
diff --git a/apps/osmpoi/custom.html b/apps/osmpoi/custom.html
index b06d0acff..6e61b68ee 100644
--- a/apps/osmpoi/custom.html
+++ b/apps/osmpoi/custom.html
@@ -216,7 +216,7 @@ g.clear();`;
 
         sendCustomizedApp({
           storage:[
-            {name:"osmpoi.app.js", content:app}
+            {name:"osmpoi.app.js", url:"app.js", content:app}
           ]
         });
       });
diff --git a/apps/qrcode/custom.html b/apps/qrcode/custom.html
index 6b288705a..9bcb79163 100644
--- a/apps/qrcode/custom.html
+++ b/apps/qrcode/custom.html
@@ -104,7 +104,7 @@ g.setColor(1,1,1);
 `;
         sendCustomizedApp({
           storage:[
-            {name:"qrcode.app.js", content:app},
+            {name:"qrcode.app.js", url:"app.js", content:app},
           ]
         });
 
diff --git a/apps/route/custom.html b/apps/route/custom.html
index 0079606b6..124c92a31 100644
--- a/apps/route/custom.html
+++ b/apps/route/custom.html
@@ -243,7 +243,7 @@ g.clear();
 
 sendCustomizedApp({
   storage:[
-    {name:"route.app.js", content:app}
+    {name:"route.app.js", url:"app.js", content:app}
   ]
 });
 });
diff --git a/core b/core
index 20a09f4f2..9708e1a15 160000
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit 20a09f4f225ad0edae5e9b52b98900ebe8ef97cc
+Subproject commit 9708e1a15ee20734a24f6f2913078aa8bba625dc