diff --git a/javascript/net/grpc/web/abstractclientbase.js b/javascript/net/grpc/web/abstractclientbase.js
index d39befcba..e1e85f8f7 100644
--- a/javascript/net/grpc/web/abstractclientbase.js
+++ b/javascript/net/grpc/web/abstractclientbase.js
@@ -46,16 +46,17 @@ const AbstractClientBase = function() {};
  * @param {function(new: RESPONSE, ...)} responseType
  * @param {function(REQUEST): ?} requestSerializeFn
  * @param {function(?): RESPONSE} responseDeserializeFn
+ * @export
  */
 AbstractClientBase.MethodInfo = function(
     responseType,
     requestSerializeFn,
     responseDeserializeFn) {
-  /** @const */
+  /** @const @export */
   this.responseType = responseType;
-  /** @const */
+  /** @const @export */
   this.requestSerializeFn = requestSerializeFn;
-  /** @const */
+  /** @const @export */
   this.responseDeserializeFn = responseDeserializeFn;
 };
 
@@ -81,6 +82,7 @@ AbstractClientBase.MethodInfo = function(
  *   callback A callback function which takes (error, response)
  * @return {!ClientReadableStream<RESPONSE_LEAN>|undefined}
  *   The Client Readable Stream
+ * @export
  */
 AbstractClientBase.prototype.rpcCall = goog.abstractMethod;
 
@@ -93,6 +95,7 @@ AbstractClientBase.prototype.rpcCall = goog.abstractMethod;
  * @param {!AbstractClientBase.MethodInfo<REQUEST, RESPONSE>}
  *   methodInfo Information of this RPC method
  * @return {!ClientReadableStream<RESPONSE>} The Client Readable Stream
+ * @export
  */
 AbstractClientBase.prototype.serverStreaming = goog.abstractMethod;
 
diff --git a/javascript/net/grpc/web/clientreadablestream.js b/javascript/net/grpc/web/clientreadablestream.js
index 0f3f0bb6d..a28d151bf 100644
--- a/javascript/net/grpc/web/clientreadablestream.js
+++ b/javascript/net/grpc/web/clientreadablestream.js
@@ -49,6 +49,7 @@ const ClientReadableStream = function() {};
  * @param {function(?)} callback The call back to handle the event with
  * an optional input object
  * @return {!ClientReadableStream} this object
+ * @export
  */
 ClientReadableStream.prototype.on = goog.abstractMethod;
 
@@ -56,6 +57,7 @@ ClientReadableStream.prototype.on = goog.abstractMethod;
 
 /**
  * Close the stream.
+ * @export
  */
 ClientReadableStream.prototype.cancel = goog.abstractMethod;
 
diff --git a/javascript/net/grpc/web/error.js b/javascript/net/grpc/web/error.js
index 79f8ec26f..fe50c3ff1 100644
--- a/javascript/net/grpc/web/error.js
+++ b/javascript/net/grpc/web/error.js
@@ -26,14 +26,13 @@ goog.module('grpc.web.Error');
 
 goog.module.declareLegacyNamespace();
 
+/** @record */
+function Error() {}
 
+/** @export @type {(number|undefined)} */
+Error.prototype.code;
 
-/**
- * @typedef {{
- *   code: (number|undefined),
- *   message: (string|undefined),
- * }}
- */
-let Error;
+/** @export @type {(string|undefined)} */
+Error.prototype.message;
 
 exports = Error;
diff --git a/javascript/net/grpc/web/gatewayclientbase.js b/javascript/net/grpc/web/gatewayclientbase.js
index 461003eb3..28b36b9be 100644
--- a/javascript/net/grpc/web/gatewayclientbase.js
+++ b/javascript/net/grpc/web/gatewayclientbase.js
@@ -46,6 +46,7 @@ const {Status} = goog.require('grpc.web.Status');
  * @param {?Object=} opt_options
  * @constructor
  * @implements {AbstractClientBase}
+ * @export
  */
 const GatewayClientBase = function(opt_options) {
 };
@@ -53,6 +54,7 @@ const GatewayClientBase = function(opt_options) {
 
 /**
  * @override
+ * @export
  */
 GatewayClientBase.prototype.rpcCall = function(
     method, request, metadata, methodInfo, callback) {
@@ -90,6 +92,7 @@ GatewayClientBase.prototype.rpcCall = function(
 
 /**
  * @override
+ * @export
  */
 GatewayClientBase.prototype.serverStreaming = function(
     method, request, metadata, methodInfo) {
@@ -176,6 +179,7 @@ GatewayClientBase.parseRpcStatus_ = function(data) {
       pair.getSecond_asU8());
     metadata[first] = second;
   }
+  /** @type {!Status} */
   var status = {
     code: rpcStatus.getCode(),
     details: rpcStatus.getMessage(),
diff --git a/javascript/net/grpc/web/grpcwebclientbase.js b/javascript/net/grpc/web/grpcwebclientbase.js
index d5ae0ef42..9836e66be 100644
--- a/javascript/net/grpc/web/grpcwebclientbase.js
+++ b/javascript/net/grpc/web/grpcwebclientbase.js
@@ -61,6 +61,7 @@ const GrpcWebClientBase = function(opt_options) {
 
 /**
  * @override
+ * @export
  */
 GrpcWebClientBase.prototype.rpcCall = function(
     method, request, metadata, methodInfo, callback) {
@@ -116,6 +117,7 @@ GrpcWebClientBase.prototype.rpcCall = function(
 
 /**
  * @override
+ * @export
  */
 GrpcWebClientBase.prototype.serverStreaming = function(
     method, request, metadata, methodInfo) {
diff --git a/javascript/net/grpc/web/grpcwebclientreadablestream.js b/javascript/net/grpc/web/grpcwebclientreadablestream.js
index a4149a7f6..eb40f141c 100644
--- a/javascript/net/grpc/web/grpcwebclientreadablestream.js
+++ b/javascript/net/grpc/web/grpcwebclientreadablestream.js
@@ -42,7 +42,7 @@ const events = goog.require('goog.events');
 const googCrypt = goog.require('goog.crypt.base64');
 const googString = goog.require('goog.string');
 const {GenericTransportInterface} = goog.require('grpc.web.GenericTransportInterface');
-const {Status} = goog.require('grpc.web.Status');
+const Status = goog.require('grpc.web.Status');
 
 
 
@@ -164,11 +164,11 @@ const GrpcWebClientReadableStream = function(genericTransportInterface) {
             grpcStatusMessage = trailers[GRPC_STATUS_MESSAGE];
           }
           if (self.onStatusCallback_) {
-            self.onStatusCallback_({
+            self.onStatusCallback_(/** @type {!Status} */({
               code: Number(grpcStatusCode),
               details: grpcStatusMessage,
               metadata: trailers,
-            });
+            }));
           }
         }
       }
@@ -207,6 +207,7 @@ const GrpcWebClientReadableStream = function(genericTransportInterface) {
 
 /**
  * @override
+ * @export
  */
 GrpcWebClientReadableStream.prototype.on = function(
     eventType, callback) {
@@ -229,6 +230,7 @@ GrpcWebClientReadableStream.prototype.on = function(
  *
  * @param {function(?):!RESPONSE} responseDeserializeFn The deserialize
  *   function for the proto
+ * @export
  */
 GrpcWebClientReadableStream.prototype.setResponseDeserializeFn =
   function(responseDeserializeFn) {
@@ -238,6 +240,7 @@ GrpcWebClientReadableStream.prototype.setResponseDeserializeFn =
 
 /**
  * @override
+ * @export
  */
 GrpcWebClientReadableStream.prototype.cancel = function() {
   this.xhr_.abort();
diff --git a/javascript/net/grpc/web/grpcwebstreamparser.js b/javascript/net/grpc/web/grpcwebstreamparser.js
index ace94dd88..5c561f522 100644
--- a/javascript/net/grpc/web/grpcwebstreamparser.js
+++ b/javascript/net/grpc/web/grpcwebstreamparser.js
@@ -131,6 +131,7 @@ Parser.State_ = {
 /**
  * Possible frame byte
  * @enum {number}
+ * @export
  */
 GrpcWebStreamParser.FrameType = {
   DATA:    0x00,   // expecting a data frame
diff --git a/javascript/net/grpc/web/status.js b/javascript/net/grpc/web/status.js
index f8ac7bd2b..04541e7d4 100644
--- a/javascript/net/grpc/web/status.js
+++ b/javascript/net/grpc/web/status.js
@@ -26,13 +26,16 @@ goog.module('grpc.web.Status');
 
 goog.module.declareLegacyNamespace();
 
+/** @record */
+function Status() {}
 
+/** @export @type {number} */
+Status.prototype.code;
 
-/**
- * @typedef {{
- *   code: number,
- *   details: string,
- *   metadata: (!Object<string, string>|undefined)
- * }}
- */
-exports.Status;
+/** @export @type {string} */
+Status.prototype.details;
+
+/** @export @type {(!Object<string, string>|undefined)} */
+Status.prototype.metadata;
+
+exports = Status;
diff --git a/javascript/net/grpc/web/statuscode.js b/javascript/net/grpc/web/statuscode.js
index 8cac2ff5c..9347263eb 100644
--- a/javascript/net/grpc/web/statuscode.js
+++ b/javascript/net/grpc/web/statuscode.js
@@ -146,6 +146,7 @@ const StatusCode = {
  * Convert HTTP Status code to gRPC Status code
  * @param {number} http_status HTTP Status Code
  * @return {number} gRPC Status Code
+ * @export
  */
 StatusCode.fromHttpStatus = function(http_status) {
   switch (http_status) {
diff --git a/javascript/net/grpc/web/streambodyclientreadablestream.js b/javascript/net/grpc/web/streambodyclientreadablestream.js
index b4bb25c0c..b1336bcb8 100644
--- a/javascript/net/grpc/web/streambodyclientreadablestream.js
+++ b/javascript/net/grpc/web/streambodyclientreadablestream.js
@@ -51,6 +51,7 @@ const {Status} = goog.require('grpc.web.Status');
  * @final
  * @param {!GenericTransportInterface} genericTransportInterface The
  *   GenericTransportInterface
+ * @export
  */
 const StreamBodyClientReadableStream = function(genericTransportInterface) {
   /**
@@ -139,6 +140,7 @@ const StreamBodyClientReadableStream = function(genericTransportInterface) {
 
 /**
  * @override
+ * @export
  */
 StreamBodyClientReadableStream.prototype.on = function(
     eventType, callback) {
@@ -161,6 +163,7 @@ StreamBodyClientReadableStream.prototype.on = function(
  *
  * @param {function(?): RESPONSE} responseDeserializeFn The deserialize
  *   function for the proto
+ * @export
  */
 StreamBodyClientReadableStream.prototype.setResponseDeserializeFn =
   function(responseDeserializeFn) {
@@ -174,6 +177,7 @@ StreamBodyClientReadableStream.prototype.setResponseDeserializeFn =
  *
  * @param {function(?):!Status} rpcStatusParseFn A function to parse
  *    the RPC status response
+ * @export
  */
 StreamBodyClientReadableStream.prototype.setRpcStatusParseFn = function(rpcStatusParseFn) {
   this.rpcStatusParseFn_ = rpcStatusParseFn;
@@ -182,6 +186,7 @@ StreamBodyClientReadableStream.prototype.setRpcStatusParseFn = function(rpcStatu
 
 /**
  * @override
+ * @export
  */
 StreamBodyClientReadableStream.prototype.cancel = function() {
   this.xhr_.abort();
diff --git a/javascript/net/grpc/web/util/genericpbjsclient.js b/javascript/net/grpc/web/util/genericpbjsclient.js
index d4fc31c57..0f05dcf08 100644
--- a/javascript/net/grpc/web/util/genericpbjsclient.js
+++ b/javascript/net/grpc/web/util/genericpbjsclient.js
@@ -40,6 +40,7 @@ var GatewayClientBase = goog.require('grpc.web.GatewayClientBase');
  * @constructor
  * @struct
  * @final
+ * @export
  */
 var GenericPbjsClient = function(hostname) {
 
@@ -62,6 +63,7 @@ var GenericPbjsClient = function(hostname) {
  *
  * @param {!Object} method The method (a Protobuf.js Method object)
  * @return {string} The full name of the service containing the method
+ * @export
  */
 function getServiceName(method) {
   var fullName = method.parent.fullName;
@@ -80,6 +82,7 @@ function getServiceName(method) {
  * @param {!Object<string, string>} metadata User defined call metadata
  * @param {function(?Error, ?Object)} callback A callback function
  *     which takes (error, response)
+ * @export
  */
 GenericPbjsClient.prototype.rpcCall = function(
     method, request, metadata, callback) {
diff --git a/packages/grpc-web/exports.js b/packages/grpc-web/exports.js
new file mode 100644
index 000000000..f3e958a6a
--- /dev/null
+++ b/packages/grpc-web/exports.js
@@ -0,0 +1,21 @@
+goog.module('grpc.web.Exports');
+
+const AbstractClientBase = goog.require('grpc.web.AbstractClientBase');
+const ClientReadableStream = goog.require('grpc.web.ClientReadableStream');
+const Error = goog.require('grpc.web.Error');
+const GrpcWebClientBase = goog.require('grpc.web.GrpcWebClientBase');
+const GrpcWebClientReadableStream = goog.require('grpc.web.GrpcWebClientReadableStream');
+const GrpcWebStreamParser = goog.require('grpc.web.GrpcWebStreamParser');
+const Status = goog.require('grpc.web.Status');
+const StatusCode = goog.require('grpc.web.StatusCode');
+
+const exports = module['exports'];
+exports['AbstractClientBase'] = AbstractClientBase;
+exports['AbstractClientBase']['MethodInfo'] = AbstractClientBase.MethodInfo;
+exports['ClientReadableStream'] = ClientReadableStream;
+exports['Error'] = Error;
+exports['GrpcWebClientBase'] = GrpcWebClientBase;
+exports['GrpcWebClientReadableStream'] = GrpcWebClientReadableStream;
+exports['GrpcWebStreamParser'] = GrpcWebStreamParser;
+exports['Status'] = Status;
+exports['StatusCode'] = StatusCode;
diff --git a/packages/grpc-web/module.js b/packages/grpc-web/module.js
new file mode 100644
index 000000000..a035483a7
--- /dev/null
+++ b/packages/grpc-web/module.js
@@ -0,0 +1,2 @@
+// Tells Closure Compiler that "module" is externally defined
+let module;
diff --git a/packages/grpc-web/scripts/build.js b/packages/grpc-web/scripts/build.js
index f8d52f90a..8fe25dd74 100644
--- a/packages/grpc-web/scripts/build.js
+++ b/packages/grpc-web/scripts/build.js
@@ -24,29 +24,21 @@ const cwd = process.cwd();
 const indexPath = path.relative(cwd, path.resolve(__dirname, "../index.js"));
 
 const jsPaths = [
+  "../exports.js",
   "../../../javascript",
   "../../../third_party/closure-library",
-  "../../../third_party/grpc/third_party/protobuf/js",
 ].map(jsPath => path.relative(cwd, path.resolve(__dirname, jsPath)));
 
-const grpcWebExports = [
-  "grpc.web.AbstractClientBase",
-  "grpc.web.ClientReadableStream",
-  "grpc.web.Error",
-  "grpc.web.GrpcWebClientBase",
-  "grpc.web.GrpcWebClientReadableStream",
-  "grpc.web.GrpcWebStreamParser",
-  "grpc.web.Status",
-  "grpc.web.StatusCode",
-];
-
 const closureArgs = [].concat(
   jsPaths.map(jsPath => `--js=${jsPath}`),
-  grpcWebExports.map(grpcWebExport => `--entry_point=${grpcWebExport}`),
   [
+    `--entry_point=grpc.web.Exports`,
+    `--externs=module.js`,
     `--dependency_mode=STRICT`,
+    `--compilation_level=ADVANCED_OPTIMIZATIONS`,
+    `--generate_exports`,
+    `--export_local_property_definitions`,
     `--js_output_file=${indexPath}`,
-    `--output_wrapper="%output%module.exports = grpc.web;"`,
   ]
 );