diff --git a/docs/static/experiments/bluetoothPartialFlashing.png b/docs/static/experiments/bluetoothPartialFlashing.png
new file mode 100644
index 00000000..6e99d685
Binary files /dev/null and b/docs/static/experiments/bluetoothPartialFlashing.png differ
diff --git a/editor/extension.ts b/editor/extension.ts
index 5de0b89e..4f570743 100644
--- a/editor/extension.ts
+++ b/editor/extension.ts
@@ -531,31 +531,27 @@ namespace pxt.editor {
         })
     }
 
-    export function deployCoreAsync(resp: pxtc.CompileResult, d: pxt.commands.DeployOptions = {}): Promise<void> {
-        const saveHexAsync = () => {
-            return pxt.commands.saveOnlyAsync(resp);
-        };
-        return Promise.resolve()
-            .then(() => {
-                const isUwp = !!(window as any).Windows;
-                if (isUwp) {
-                    // Go straight to flashing
+    function uwpDeployCoreAsync(resp: pxtc.CompileResult, d: pxt.commands.DeployOptions = {}): Promise<void> {
+        // Go straight to flashing
+        return flashAsync(resp, d);
+    }
+
+    function deployCoreAsync(resp: pxtc.CompileResult, d: pxt.commands.DeployOptions = {}): Promise<void> {
+        return pxt.usb.isPairedAsync()
+            .then(isPaired => {
+                if (isPaired) {
+                    // Already paired from earlier in the session or from previous session
                     return flashAsync(resp, d);
                 }
-                if (!pxt.usb.isEnabled) {
-                    return saveHexAsync();
-                }
-                return pxt.usb.isPairedAsync()
-                    .then((isPaired) => {
-                        if (isPaired) {
-                            // Already paired from earlier in the session or from previous session
-                            return flashAsync(resp, d);
-                        }
 
-                        // No device paired, prompt user
-                        return saveHexAsync();
-                    });
-            })
+                // try bluetooth if device is paired
+                if (pxt.webBluetooth.isPaired())
+                    return pxt.webBluetooth.flashAsync(resp, d)
+                        .catch(e => pxt.commands.saveOnlyAsync(resp));
+
+                // No device paired, prompt user
+                return pxt.commands.saveOnlyAsync(resp);
+            });
     }
 
     /**
@@ -820,7 +816,10 @@ namespace pxt.editor {
             subclassCode: 0x03
         }])
 
-        if (canHID())
+        const isUwp = !!(window as any).Windows;
+        if (isUwp)
+            pxt.commands.deployCoreAsync = uwpDeployCoreAsync;
+        else if (canHID() || pxt.webBluetooth.hasPartialFlash())
             pxt.commands.deployCoreAsync = deployCoreAsync;
 
         res.blocklyPatch = patchBlocks;
diff --git a/libs/core/pxt.json b/libs/core/pxt.json
index cca2f32f..273db610 100644
--- a/libs/core/pxt.json
+++ b/libs/core/pxt.json
@@ -72,7 +72,7 @@
                     "microbit-dal": {
                         "bluetooth": {
                             "open": 1,
-                            "pairing_mode": 0,
+                            "pairing_mode": null,
                             "whitelist": 0,
                             "security_level": null
                         }
@@ -98,7 +98,7 @@
                     "microbit-dal": {
                         "bluetooth": {
                             "open": 0,
-                            "pairing_mode": 1,
+                            "pairing_mode": null,
                             "whitelist": 1,
                             "security_level": "SECURITY_MODE_ENCRYPTION_WITH_MITM"
                         }
diff --git a/package.json b/package.json
index 543c05e1..fcd36f1d 100644
--- a/package.json
+++ b/package.json
@@ -38,10 +38,11 @@
     "@types/bluebird": "2.0.33",
     "@types/jquery": "3.2.16",
     "@types/marked": "0.3.0",
-    "@types/node": "8.0.53"
+    "@types/node": "8.0.53",
+    "@types/web-bluetooth": "0.0.4"
   },
   "dependencies": {
     "pxt-common-packages": "0.24.2",
-    "pxt-core": "4.1.28"
+    "pxt-core": "4.1.30"
   }
 }
diff --git a/pxtarget.json b/pxtarget.json
index 29b3f709..bcac50c6 100644
--- a/pxtarget.json
+++ b/pxtarget.json
@@ -275,7 +275,8 @@
             "allowPackageExtensions",
             "instructions",
             "debugger",
-            "bluetoothUartConsole"
+            "bluetoothUartConsole",
+            "bluetoothPartialFlashing"
         ],
         "bluetoothUartFilters": [{
             "namePrefix": "BBC micro:bit"