diff --git a/bin/thumbnailer.js b/bin/thumbnailer.js
index 922217fb2..db658b01e 100755
--- a/bin/thumbnailer.js
+++ b/bin/thumbnailer.js
@@ -2,15 +2,18 @@
 
 var EMULATOR = "banglejs1";
 
-var appId;
+var singleAppId;
 
-if (process.argv.length!=3) {
+if (process.argv.length!=3 && process.argv.length!=2) {
   console.log("USAGE:");
-  console.log("  bin/thumbnailer.jd APP_ID");
+  console.log("  bin/thumbnailer.js");
+  console.log("    - all thumbnails");
+  console.log("  bin/thumbnailer.js APP_ID");
+  console.log("    - just one app");
   process.exit(1);
 }
-appId = process.argv[2];
-imageFn = "out.png";
+if (process.argv.length==3)
+  singleAppId = process.argv[2];
 
 if (!require("fs").existsSync(__dirname + "/../../EspruinoWebIDE")) {
   console.log("You need to:");
@@ -33,52 +36,106 @@ eval(require("fs").readFileSync(__dirname + "/../core/lib/espruinotools.js").toS
 eval(require("fs").readFileSync(__dirname + "/../core/js/utils.js").toString());
 eval(require("fs").readFileSync(__dirname + "/../core/js/appinfo.js").toString());
 var apps = JSON.parse(require("fs").readFileSync(__dirname+"/../apps.json"));
-var app = apps.find(a=>a.id==appId);
-if (!app) ERROR(`App ${JSON.stringify(appId)} not found`);
-if (app.custom) ERROR(`App ${JSON.stringify(appId)} requires HTML customisation`);
 
+/* we factory reset ONCE, get this, then we can use it to reset
+state quickly for each new app */
+var factoryFlashMemory = new Uint8Array(FLASH_SIZE);
 
 jsRXCallback = function() {};
 jsUpdateGfx = function() {};
 
+function ERROR(s) {
+  console.error(s);
+  process.exit(1);
+}
+
+function getThumbnail(appId, imageFn) {
+  console.log("Thumbnail for "+appId);
+  var app = apps.find(a=>a.id==appId);
+  if (!app) ERROR(`App ${JSON.stringify(appId)} not found`);
+  if (app.custom) ERROR(`App ${JSON.stringify(appId)} requires HTML customisation`);
+
+
+  return new Promise(resolve => {
+    AppInfo.getFiles(app, {
+      fileGetter:function(url) {
+        console.log(__dirname+"/"+url);
+        return Promise.resolve(require("fs").readFileSync(__dirname+"/../"+url).toString("binary"));
+      }, settings : SETTINGS}).then(files => {
+        console.log("AppInfo returned");//, files);
+        flashMemory.set(factoryFlashMemory);
+        jsTransmitString("reset()\n");
+        console.log("Uploading...");
+        jsTransmitString("g.clear()\n");
+        var command = files.map(f=>f.cmd).join("\n")+"\n";
+        command += `load("${appId}.app.js")\n`;
+        jsTransmitString(command);
+        console.log("Done.");
+        jsStopIdle();
+
+        var rgba = new Uint8Array(GFX_WIDTH*GFX_HEIGHT*4);
+        jsGetGfxContents(rgba);
+        var rgba32 = new Uint32Array(rgba.buffer);
+        var firstPixel = rgba32[0];
+        var blankImage = rgba32.every(col=>col==firstPixel)
+
+        if (!blankImage) {
+          var Jimp = require("jimp");
+          let image = new Jimp(GFX_WIDTH, GFX_HEIGHT, function (err, image) {
+            if (err) throw err;
+            let buffer = image.bitmap.data;
+            buffer.set(rgba);
+            image.write(imageFn, (err) => {
+              if (err) throw err;
+              console.log("Image written as "+imageFn);
+              resolve(true);
+            });
+          });
+        } else {
+          console.log("Image is empty");
+          resolve(false);
+        }
+
+      });
+    });
+}
+
+var screenshots = [];
+
 // wait until loaded...
 setTimeout(function() {
   console.log("Loaded...");
   jsInit();
-  jsIdle(true); // not automatic
-  
-  AppInfo.getFiles(app, {
-    fileGetter:function(url) {
-      console.log(__dirname+"/"+url);
-      return Promise.resolve(require("fs").readFileSync(__dirname+"/../"+url).toString("binary"));
-    }, settings : SETTINGS}).then(files => {
-      //console.log(files);
-      var command = "Bangle.factoryReset()\n";
-      command += files.map(f=>f.cmd).join("\n")+"\n";
-      command += `load("${appId}.app.js")\n`;
-      //console.log(command);
-      console.log("Uploading...");
-      jsTransmitString(command);
-      console.log("Done.");
-      jsIdle();
-      jsIdle();
-      jsIdle();
-      jsStopIdle();
-      
-      var rgba = new Uint8Array(GFX_WIDTH*GFX_HEIGHT*4);
-      jsGetGfxContents(rgba);
-      
-      var Jimp = require("jimp");
-      let image = new Jimp(GFX_WIDTH, GFX_HEIGHT, function (err, image) {
-        if (err) throw err;
-        let buffer = image.bitmap.data;
-        buffer.set(rgba);
-        image.write(imageFn, (err) => {
-          if (err) throw err;
-          console.log("Image written as "+imageFn);
+  jsIdle();
+  console.log("Factory reset");
+  jsTransmitString("Bangle.factoryReset()\n");
+  factoryFlashMemory.set(flashMemory);
+  console.log("Ready!");
+
+  if (singleAppId) {
+    getThumbnail(singleAppId, "screenshots/"+singleAppId+".png")
+
+    return;
+  }
+
+  var appList = apps.filter(app => (!app.type || app.type=="clock") && !app.custom).map(app=>app.id);
+  // TODO: Work out about Bangle.js 1 or 2
+  var promise = Promise.resolve();
+  appList.forEach(appId => {
+    promise = promise.then(() => {
+      return getThumbnail(appId, "screenshots/"+appId+".png").then(ok => {
+        screenshots.push({
+          id : appId,
+          url : "screenshots/"+appId+".png"
         });
       });
-});
-  
-  
+    });
+  });
+
+  promise.then(function() {
+    console.log("Complete!");
+    require("fs").writeFileSync("screenshots.json", JSON.stringify(screenshots,null,2));
+  });
+
+
 });