diff --git a/Examples/UIExplorer/UIExplorer/AppDelegate.m b/Examples/UIExplorer/UIExplorer/AppDelegate.m
index d56ac42a7..75a24b172 100644
--- a/Examples/UIExplorer/UIExplorer/AppDelegate.m
+++ b/Examples/UIExplorer/UIExplorer/AppDelegate.m
@@ -73,9 +73,11 @@
 }
 
 - (void)loadSourceForBridge:(RCTBridge *)bridge
-                  withBlock:(RCTSourceLoadBlock)loadCallback
+                 onProgress:(RCTSourceLoadProgressBlock)onProgress
+                 onComplete:(RCTSourceLoadBlock)loadCallback
 {
   [RCTJavaScriptLoader loadBundleAtURL:[self sourceURLForBridge:bridge]
+                            onProgress:onProgress
                             onComplete:loadCallback];
 }
 
diff --git a/React/Base/RCTBatchedBridge.m b/React/Base/RCTBatchedBridge.m
index 5e3f2572b..80df61ff7 100644
--- a/React/Base/RCTBatchedBridge.m
+++ b/React/Base/RCTBatchedBridge.m
@@ -24,6 +24,7 @@
 #import "RCTSourceCode.h"
 #import "RCTUtils.h"
 #import "RCTRedBox.h"
+#import "RCTDevLoadingView.h"
 
 #define RCTAssertJSThread() \
   RCTAssert(![NSStringFromClass([self->_javaScriptExecutor class]) isEqualToString:@"RCTJSCExecutor"] || \
@@ -115,6 +116,11 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithDelegate:(id<RCTBridgeDelegate>)dele
 
     sourceCode = source;
     dispatch_group_leave(initModulesAndLoadSource);
+  } onProgress:^(RCTLoadingProgress *progressData) {
+#ifdef RCT_DEV
+    RCTDevLoadingView *loadingView = [weakSelf moduleForClass:[RCTDevLoadingView class]];
+    [loadingView updateProgress:progressData];
+#endif
   }];
 
   // Synchronously initialize all native modules that cannot be loaded lazily
@@ -172,7 +178,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithDelegate:(id<RCTBridgeDelegate>)dele
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
 }
 
-- (void)loadSource:(RCTSourceLoadBlock)_onSourceLoad
+- (void)loadSource:(RCTSourceLoadBlock)_onSourceLoad onProgress:(RCTSourceLoadProgressBlock)onProgress
 {
   [_performanceLogger markStartForTag:RCTPLScriptDownload];
 
@@ -183,18 +189,20 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithDelegate:(id<RCTBridgeDelegate>)dele
     _onSourceLoad(error, source, sourceLength);
   };
 
-  if ([self.delegate respondsToSelector:@selector(loadSourceForBridge:withBlock:)]) {
+  if ([self.delegate respondsToSelector:@selector(loadSourceForBridge:onProgress:onComplete:)]) {
+    [self.delegate loadSourceForBridge:_parentBridge onProgress:onProgress onComplete:onSourceLoad];
+  } else if ([self.delegate respondsToSelector:@selector(loadSourceForBridge:withBlock:)]) {
     [self.delegate loadSourceForBridge:_parentBridge withBlock:onSourceLoad];
   } else {
     RCTAssert(self.bundleURL, @"bundleURL must be non-nil when not implementing loadSourceForBridge");
 
-    [RCTJavaScriptLoader loadBundleAtURL:self.bundleURL onComplete:^(NSError *error, NSData *source, int64_t sourceLength) {
+    [RCTJavaScriptLoader loadBundleAtURL:self.bundleURL onProgress:onProgress onComplete:^(NSError *error, NSData *source, int64_t sourceLength) {
       if (error && [self.delegate respondsToSelector:@selector(fallbackSourceURLForBridge:)]) {
         NSURL *fallbackURL = [self.delegate fallbackSourceURLForBridge:self->_parentBridge];
         if (fallbackURL && ![fallbackURL isEqual:self.bundleURL]) {
           RCTLogError(@"Failed to load bundle(%@) with error:(%@)", self.bundleURL, error.localizedDescription);
           self.bundleURL = fallbackURL;
-          [RCTJavaScriptLoader loadBundleAtURL:self.bundleURL onComplete:onSourceLoad];
+          [RCTJavaScriptLoader loadBundleAtURL:self.bundleURL onProgress:onProgress onComplete:onSourceLoad];
           return;
         }
       }
diff --git a/React/Base/RCTBridgeDelegate.h b/React/Base/RCTBridgeDelegate.h
index f866c94cf..c5f0cdb40 100644
--- a/React/Base/RCTBridgeDelegate.h
+++ b/React/Base/RCTBridgeDelegate.h
@@ -87,6 +87,14 @@
  * location specified by the `sourceURLForBridge:` method, however, if you want
  * to handle loading the JS yourself, you can do so by implementing this method.
  */
+- (void)loadSourceForBridge:(RCTBridge *)bridge
+                 onProgress:(RCTSourceLoadProgressBlock)onProgress
+                 onComplete:(RCTSourceLoadBlock)loadCallback;
+
+/**
+ * Similar to loadSourceForBridge:onProgress:onComplete: but without progress
+ * reporting.
+ */
 - (void)loadSourceForBridge:(RCTBridge *)bridge
                   withBlock:(RCTSourceLoadBlock)loadCallback;
 
diff --git a/React/Base/RCTJavaScriptLoader.h b/React/Base/RCTJavaScriptLoader.h
index 141649556..4c5b962ad 100755
--- a/React/Base/RCTJavaScriptLoader.h
+++ b/React/Base/RCTJavaScriptLoader.h
@@ -23,11 +23,20 @@ NS_ENUM(NSInteger) {
   RCTJavaScriptLoaderErrorCannotBeLoadedSynchronously = 1000,
 };
 
+@interface RCTLoadingProgress : NSObject
+
+@property (nonatomic, copy) NSString *status;
+@property (strong, nonatomic) NSNumber *done;
+@property (strong, nonatomic) NSNumber *total;
+
+@end
+
+typedef void (^RCTSourceLoadProgressBlock)(RCTLoadingProgress *progressData);
 typedef void (^RCTSourceLoadBlock)(NSError *error, NSData *source, int64_t sourceLength);
 
 @interface RCTJavaScriptLoader : NSObject
 
-+ (void)loadBundleAtURL:(NSURL *)scriptURL onComplete:(RCTSourceLoadBlock)onComplete;
++ (void)loadBundleAtURL:(NSURL *)scriptURL onProgress:(RCTSourceLoadProgressBlock)onProgress onComplete:(RCTSourceLoadBlock)onComplete;
 
 /**
  * @experimental
diff --git a/React/Base/RCTJavaScriptLoader.m b/React/Base/RCTJavaScriptLoader.m
index cb19dce80..58988920a 100755
--- a/React/Base/RCTJavaScriptLoader.m
+++ b/React/Base/RCTJavaScriptLoader.m
@@ -22,11 +22,27 @@ uint32_t const RCTRAMBundleMagicNumber = 0xFB0BD1E5;
 
 NSString *const RCTJavaScriptLoaderErrorDomain = @"RCTJavaScriptLoaderErrorDomain";
 
+@implementation RCTLoadingProgress
+
+- (NSString *)description
+{
+  NSMutableString *desc = [NSMutableString new];
+  [desc appendString:_status ?: @"Loading"];
+
+  if (_total > 0) {
+    [desc appendFormat:@" %ld%% (%@/%@)", (long)(100 * [_done integerValue] / [_total integerValue]), _done, _total];
+  }
+  [desc appendString:@"…"];
+  return desc;
+}
+
+@end
+
 @implementation RCTJavaScriptLoader
 
 RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
-+ (void)loadBundleAtURL:(NSURL *)scriptURL onComplete:(RCTSourceLoadBlock)onComplete
++ (void)loadBundleAtURL:(NSURL *)scriptURL onProgress:(RCTSourceLoadProgressBlock)onProgress onComplete:(RCTSourceLoadBlock)onComplete
 {
   int64_t sourceLength;
   NSError *error;
@@ -43,7 +59,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   && error.code == RCTJavaScriptLoaderErrorCannotBeLoadedSynchronously;
 
   if (isCannotLoadSyncError) {
-    attemptAsynchronousLoadOfBundleAtURL(scriptURL, onComplete);
+    attemptAsynchronousLoadOfBundleAtURL(scriptURL, onProgress, onComplete);
   } else {
     onComplete(error, nil, 0);
   }
@@ -136,7 +152,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   return [NSData dataWithBytes:&magicNumber length:sizeof(magicNumber)];
 }
 
-static void attemptAsynchronousLoadOfBundleAtURL(NSURL *scriptURL, RCTSourceLoadBlock onComplete)
+static void attemptAsynchronousLoadOfBundleAtURL(NSURL *scriptURL, RCTSourceLoadProgressBlock onProgress, RCTSourceLoadBlock onComplete)
 {
   scriptURL = sanitizeURL(scriptURL);
 
@@ -155,7 +171,9 @@ static void attemptAsynchronousLoadOfBundleAtURL(NSURL *scriptURL, RCTSourceLoad
 
   RCTMultipartDataTask *task = [[RCTMultipartDataTask alloc] initWithURL:scriptURL partHandler:^(NSInteger statusCode, NSDictionary *headers, NSData *data, NSError *error, BOOL done) {
     if (!done) {
-      // TODO(frantic): Emit progress event
+      if (onProgress) {
+        onProgress(progressEventFromData(data));
+      }
       return;
     }
 
@@ -206,6 +224,21 @@ static NSURL *sanitizeURL(NSURL *url)
   return [RCTConvert NSURL:url.absoluteString];
 }
 
+static RCTLoadingProgress *progressEventFromData(NSData *rawData)
+{
+  NSString *text = [[NSString alloc] initWithData:rawData encoding:NSUTF8StringEncoding];
+  id info = RCTJSONParse(text, nil);
+  if (!info || ![info isKindOfClass:[NSDictionary class]]) {
+    return nil;
+  }
+
+  RCTLoadingProgress *progress = [RCTLoadingProgress new];
+  progress.status = [info valueForKey:@"status"];
+  progress.done = [info valueForKey:@"done"];
+  progress.total = [info valueForKey:@"total"];
+  return progress;
+}
+
 static NSDictionary *userInfoForRawResponse(NSString *rawText)
 {
   NSDictionary *parsedResponse = RCTJSONParse(rawText, nil);
diff --git a/React/Modules/RCTDevLoadingView.h b/React/Modules/RCTDevLoadingView.h
index b09315fb6..2d9f15c4a 100644
--- a/React/Modules/RCTDevLoadingView.h
+++ b/React/Modules/RCTDevLoadingView.h
@@ -12,5 +12,6 @@
 @interface RCTDevLoadingView : NSObject <RCTBridgeModule>
 
 + (void)setEnabled:(BOOL)enabled;
+- (void)updateProgress:(RCTLoadingProgress *)progress;
 
 @end
diff --git a/React/Modules/RCTDevLoadingView.m b/React/Modules/RCTDevLoadingView.m
index 0b7ee4996..89f645ff8 100644
--- a/React/Modules/RCTDevLoadingView.m
+++ b/React/Modules/RCTDevLoadingView.m
@@ -142,6 +142,16 @@ RCT_EXPORT_METHOD(hide)
     backgroundColor:backgroundColor];
 }
 
+- (void)updateProgress:(RCTLoadingProgress *)progress
+{
+  if (!progress) {
+    return;
+  }
+  dispatch_async(dispatch_get_main_queue(), ^{
+    self->_label.text = [progress description];
+  });
+}
+
 @end
 
 #else
@@ -150,6 +160,7 @@ RCT_EXPORT_METHOD(hide)
 
 + (NSString *)moduleName { return nil; }
 + (void)setEnabled:(BOOL)enabled { }
+- (void)updateProgress:(RCTLoadingProgress *)progress {}
 
 @end