diff --git a/sdk/build.gradle b/sdk/build.gradle
index 9dc17505..2fab4a89 100644
--- a/sdk/build.gradle
+++ b/sdk/build.gradle
@@ -11,7 +11,7 @@ plugins {
 }
 
 ext {
-    hcaptchaLoaderVersion = "1.1.3"
+    hcaptchaLoaderVersion = "1.2.3"
 }
 
 android {
@@ -117,14 +117,20 @@ project.afterEvaluate {
     }
 }
 
-long MAX_AAR_SIZE_KB = 200
+long MAX_AAR_SIZE_KB = 250
 
-tasks.register('downloadHCaptchaLoaderJs', Download) {
-    src "https://www.unpkg.com/@hcaptcha/loader@${hcaptchaLoaderVersion}/dist/index.mjs"
-    dest layout.buildDirectory.file("generated/assets/hcaptcha/loader.mjs")
+tasks.register('downloadPolyfillsJs', Download) {
+    src "https://www.unpkg.com/@hcaptcha/loader@${hcaptchaLoaderVersion}/dist/polyfills.js"
+    dest layout.buildDirectory.file("generated/assets/hcaptcha/polyfills.js")
     onlyIfModified true
 }
 
+tasks.register('downloadHCaptchaLoaderJs', Download) {
+    src "https://www.unpkg.com/@hcaptcha/loader@${hcaptchaLoaderVersion}/dist/index.es5.js"
+    dest layout.buildDirectory.file("generated/assets/hcaptcha/loader.js")
+    onlyIfModified true
+}.get().dependsOn('downloadPolyfillsJs')
+
 android.sourceSets.main.assets.srcDirs += [layout.buildDirectory.file("generated/assets")]
 
 android.libraryVariants.all { variant ->
@@ -150,7 +156,7 @@ android.libraryVariants.all { variant ->
             var aarFile = variant.packageLibraryProvider.get().archiveFile.get().getAsFile()
             long aarSizeKb = aarFile.length() / 1024
             if (aarSizeKb > MAX_AAR_SIZE_KB) {
-                throw new GradleException("${aarPath} size exceeded! ${aarSizeKb}Kbyte > ${MAX_AAR_SIZE_KB}Kbyte")
+                throw new GradleException("${aarFile} size exceeded! ${aarSizeKb}Kbyte > ${MAX_AAR_SIZE_KB}Kbyte")
             }
         }
     })
diff --git a/sdk/src/main/html/hcaptcha.html b/sdk/src/main/html/hcaptcha.html
index 99d15c81..a200fc20 100644
--- a/sdk/src/main/html/hcaptcha.html
+++ b/sdk/src/main/html/hcaptcha.html
@@ -36,9 +36,9 @@
         window.sysDebug = JSON.parse(window.JSDI.getSysDebug());
     }
 </script>
-<script type="module">
-    import { hCaptchaLoader } from 'https://www.unpkg.com/@hcaptcha/loader@@LOADER_VERSION@/dist/index.mjs';
-
+<script type="text/javascript" src="https://unpkg.com/@hcaptcha/loader@@LOADER_VERSION@/dist/polyfills.js"></script>
+<script type="text/javascript" src="https://unpkg.com/@hcaptcha/loader@@LOADER_VERSION@/dist/index.es5.js"></script>
+<script>
     // Android will inject this bridge object as `JSInterface`
     // Browser is missing it, so we mock it
     var BridgeObject = window.JSInterface || {
@@ -75,9 +75,9 @@
     /**
      * Called programmatically from HCaptchaWebViewHelper.
      */
-    async function resetAndExecute() {
+    function resetAndExecute() {
         hcaptcha.reset();
-        await execute();
+        execute();
     }
     window.resetAndExecute = resetAndExecute;
     function reset() {
@@ -175,17 +175,16 @@
             BridgeObject.onError(30);
         }
     });
-    async function execute() {
-        try {
-            var { response } = await hcaptcha.execute(getScriptParams(bridgeConfig));
+    function execute() {
+        hcaptcha.execute(getScriptParams(bridgeConfig)).then(function(result) {
+            var response = result.response;
             BridgeObject.onPass(response);
-        } catch (error) {
+        }).catch(function(error) {
             errorCallback(error);
-        }
+        });
     }
-    async function loadApi(config) {
-        try {
-            window.hcaptcha = await hCaptchaLoader(getLoaderParams(config));
+    function loadApi(config) {
+        hCaptchaLoader(getLoaderParams(config)).then(function(hcaptcha) {
             var renderConfig = getRenderConfig(config);
             hcaptcha.render("hcaptcha-container", renderConfig);
             BridgeObject.onLoaded();
@@ -197,12 +196,12 @@
                 // We want to auto execute in case of `invisible` checkbox.
                 // But not in case of `hideDialog` since verification process
                 // might be desired to happen at a later time.
-                await execute();
+                execute();
             }
-        } catch (e) {
-            console.error("loadApi error", e);
+        }).catch(function(error) {
+            console.error("loadApi error", error);
             BridgeObject.onError(29);
-        }
+        });
     }
     loadApi(bridgeConfig);
 </script>
diff --git a/sdk/src/main/java/com/hcaptcha/sdk/HCaptchaWebViewHelper.java b/sdk/src/main/java/com/hcaptcha/sdk/HCaptchaWebViewHelper.java
index 3dcfbd7f..c2819aa2 100644
--- a/sdk/src/main/java/com/hcaptcha/sdk/HCaptchaWebViewHelper.java
+++ b/sdk/src/main/java/com/hcaptcha/sdk/HCaptchaWebViewHelper.java
@@ -24,6 +24,8 @@
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.Objects;
 
 final class HCaptchaWebViewHelper {
@@ -124,15 +126,17 @@ public boolean shouldRetry(HCaptchaException exception) {
 
     @RequiresApi(Build.VERSION_CODES.LOLLIPOP)
     private class HCaptchaWebClient extends WebViewClient {
-        private final Uri loaderUri = Uri.parse(
-                "https://www.unpkg.com/@hcaptcha/loader@" + BuildConfig.LOADER_VERSION + "/dist/index.mjs"
-        );
+        private final Map<Uri, String> assetsCache = new HashMap<>();
 
         @NonNull
         private final Handler handler;
 
         HCaptchaWebClient(@NonNull Handler handler) {
             this.handler = handler;
+
+            final String baseUrl = "https://unpkg.com/@hcaptcha/loader@" + BuildConfig.LOADER_VERSION + "/dist";
+            assetsCache.put(Uri.parse(baseUrl + "/index.es5.js"), "hcaptcha/loader.js");
+            assetsCache.put(Uri.parse(baseUrl + "/polyfills.js"), "hcaptcha/polyfills.js");
         }
 
         private String stripUrl(String url) {
@@ -142,7 +146,8 @@ private String stripUrl(String url) {
         @Override
         public WebResourceResponse shouldInterceptRequest (final WebView view, final WebResourceRequest request) {
             final Uri requestUri = request.getUrl();
-            if (loaderUri.equals(requestUri)) {
+            final String assetPath = assetsCache.get(requestUri);
+            if (assetPath != null) {
                 try {
                     return new WebResourceResponse(
                             "application/javascript",
@@ -151,10 +156,10 @@ public WebResourceResponse shouldInterceptRequest (final WebView view, final Web
                             "OK",
                             Collections.singletonMap("Access-Control-Allow-Origin",
                                     Objects.toString(config.getHost(), "null")),
-                            view.getContext().getAssets().open("hcaptcha/loader.mjs")
+                            view.getContext().getAssets().open(assetPath)
                     );
                 } catch (IOException e) {
-                    HCaptchaLog.w("WebViewHelper wasn't able to load loader.mjs from assets");
+                    HCaptchaLog.w("WebViewHelper wasn't able to load " + assetPath + " from assets");
                 }
             } else if (requestUri != null && requestUri.getScheme() != null && requestUri.getScheme().equals("http")) {
                 handler.post(() -> {
diff --git a/test/src/androidTest/java/com/hcaptcha/sdk/HCaptchaWebViewHelperTest.java b/test/src/androidTest/java/com/hcaptcha/sdk/HCaptchaWebViewHelperTest.java
index db214820..259ff4bc 100644
--- a/test/src/androidTest/java/com/hcaptcha/sdk/HCaptchaWebViewHelperTest.java
+++ b/test/src/androidTest/java/com/hcaptcha/sdk/HCaptchaWebViewHelperTest.java
@@ -7,11 +7,13 @@
 import static org.mockito.Mockito.mock;
 
 import android.content.Context;
+import android.content.res.AssetManager;
 import android.app.Activity;
 import android.os.Handler;
 import android.os.Looper;
 
 import androidx.test.core.app.ActivityScenario;
+import androidx.test.core.app.ApplicationProvider;
 import androidx.test.ext.junit.rules.ActivityScenarioRule;
 import androidx.test.platform.app.InstrumentationRegistry;
 
@@ -22,6 +24,7 @@
 import org.junit.Test;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
@@ -95,7 +98,19 @@ public void onFailure(HCaptchaException e) {
 
     @Test
     public void testLoaderJsAssetPresence() throws IOException {
-        Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();
-        assertNotNull(appContext.getAssets().open("hcaptcha/loader.mjs"));
+        AssetManager assets = InstrumentationRegistry
+                .getInstrumentation()
+                .getTargetContext()
+                .getAssets();
+        assertNotNull(assets.open("hcaptcha/loader.js"));
+    }
+
+    @Test
+    public void testPolyfillsJsAssetPresence() throws IOException {
+        AssetManager assets = InstrumentationRegistry
+                .getInstrumentation()
+                .getTargetContext()
+                .getAssets();
+        assertNotNull(assets.open("hcaptcha/polyfills.js"));
     }
 }