diff --git a/docs/WiFi.md b/docs/WiFi.md
index ba4c1d5a..51ab773d 100644
--- a/docs/WiFi.md
+++ b/docs/WiFi.md
@@ -112,6 +112,8 @@ Browsers decompress the pages automatically over ordinary HTTP. WebConfig
 returns HTTP 406 when a client explicitly excludes gzip. Its large page closes
 the TCP connection gracefully after the final acknowledged bytes so browsers
 do not report a completed download as aborted.
+The bootstrap uses ES5 syntax and Promise-based loading, including on Android
+5.1.1 with Chrome 43; newer JavaScript syntax must not prevent the page loading.
 
 Most full-size ESP32 MQTT observer builds have the shared WebConfig portal. On a
 fresh device with no saved SSID:
diff --git a/scripts/generate_webconfig_html.py b/scripts/generate_webconfig_html.py
index 1feb56cd..b70bec3f 100644
--- a/scripts/generate_webconfig_html.py
+++ b/scripts/generate_webconfig_html.py
@@ -135,16 +135,19 @@ def main():
     loader = ("<!doctype html><meta charset=utf-8><meta name=viewport "
               "content=\"width=device-width,initial-scale=1\"><title>MeshCore "
               "WebConfig</title><body>Loading MeshCore WebConfig&hellip;<script>"
-              "(async()=>{let p;for(let n=0;n<3&&p===undefined;n++){const C="
-              "window.AbortController,c=C&&new C(),t=c&&setTimeout(()=>c.abort()"
-              ",90000);try{const r=await fetch(\"/ui?v=%s\",c?{signal:c.signal}"
-              ":{});if(r.ok)p=await r.text();else if(r.status===409)return "
-              "location.reload()}catch(e){}finally{if(t)clearTimeout(t)}if(p==="
-              "undefined)await new Promise(r=>setTimeout(r,500*(n+1)))}if(p==="
-              "undefined)throw Error(\"transfer failed\");document.open();"
-              "document.write(p);document.close()})().catch(e=>"
+              # Android 5.1's stock Chrome 43 supports fetch and Promises, but
+              # cannot parse arrows or async functions. Match the main UI's
+              # ES5 syntax so the bootstrap cannot strand those browsers.
+              "(function(){var n=0;function load(){var C=window.AbortController,"
+              "c=C&&new C(),t=c&&setTimeout(function(){c.abort()},90000);"
+              "fetch(\"/ui?v=%s\",c?{signal:c.signal}:{}).then(function(r){"
+              "if(r.ok)return r.text();if(r.status===409){location.reload();"
+              "return null}throw Error(\"transfer failed\")}).then(function(p){"
+              "if(t)clearTimeout(t);if(p===null)return;document.open();"
+              "document.write(p);document.close()},function(e){"
+              "if(t)clearTimeout(t);if(++n<3)setTimeout(load,500*n);else "
               "document.body.textContent=\"Unable to load WebConfig: \"+e+"
-              "\". Reload to retry.\")</script>" % version)
+              "\". Reload to retry.\"})}load()})()</script>" % version)
     loader_bytes = compress_page(loader.encode("utf-8"))
     success_bytes = compress_page(b"<HTML><HEAD><TITLE>Success</TITLE></HEAD><BODY>Success</BODY></HTML>")
     etag = hashlib.sha256(loader_bytes).hexdigest()[:16]
diff --git a/src/helpers/esp32/WebConfigHtml.h b/src/helpers/esp32/WebConfigHtml.h
index cdbae614..6d49c7d5 100644
--- a/src/helpers/esp32/WebConfigHtml.h
+++ b/src/helpers/esp32/WebConfigHtml.h
@@ -7,42 +7,40 @@
 #include <pgmspace.h>
 
 const uint32_t WEBCONFIG_HTML_GZ_LEN = 33969;
-const char WEBCONFIG_HTML_ETAG[] = "\"96a1dfcd38a0ae5a\"";
+const char WEBCONFIG_HTML_ETAG[] = "\"25ca2f61b991b105\"";
 const char WEBCONFIG_HTML_VERSION[] = "4d14ae4de3268605";
-const uint16_t WEBCONFIG_HTML_LOADER_LEN = 493;
+const uint16_t WEBCONFIG_HTML_LOADER_LEN = 462;
 const uint16_t WEBCONFIG_HTML_SUCCESS_LEN = 65;
 const uint8_t WEBCONFIG_HTML_LOADER[] PROGMEM = {
-  0x1f,0x8b,0x08,0x00,0x00,0x00,0x00,0x00,0x02,0xff,0xb2,0x51,0x4c,0x01,0xb4,0x49,
-  0x1d,0xcb,0x91,0xc2,0x40,0xf4,0x57,0x54,0x0e,0x94,0x34,0x79,0x9c,0x6d,0x10,0x1b,
-  0xa8,0x3d,0x6d,0xce,0x67,0x8d,0x68,0x8c,0x6a,0x85,0x44,0xb5,0x1a,0xe3,0xf8,0xef,
-  0x2b,0x9c,0x53,0x5f,0x3a,0xe7,0xe7,0x35,0x9d,0xb5,0xc0,0x6a,0x6a,0x6c,0x9e,0x35,
-  0x40,0x8a,0xe9,0x5a,0x61,0x00,0x92,0x1d,0x55,0xd3,0x83,0x5b,0x9b,0x53,0x0d,0xc8,
-  0x13,0x03,0x7d,0xeb,0x91,0x98,0xf6,0x8e,0xc0,0x91,0x5c,0xeb,0x4d,0x49,0xb5,0x2c,
-  0xe1,0xc4,0x68,0x98,0x5e,0x2b,0x13,0xe3,0x0c,0x19,0x65,0xa7,0x41,0x2b,0x0b,0x72,
-  0xb9,0x96,0x67,0x64,0xc8,0x42,0xfe,0x19,0x42,0x5d,0x78,0x04,0xf6,0x17,0x56,0x85,
-  0x77,0x95,0x39,0xce,0xe6,0x37,0x9e,0x6c,0xe5,0xcb,0xb3,0xfc,0x93,0x57,0xa5,0x71,
-  0xc7,0xec,0x65,0x5c,0x52,0x83,0xb5,0xa6,0x4d,0xb3,0xa0,0xd1,0xb4,0x94,0x73,0x15,
-  0xce,0x9c,0xe6,0x42,0xe6,0x17,0x16,0x88,0xb5,0x69,0xe5,0x91,0x0f,0x92,0x93,0x8b,
-  0xd4,0x65,0xdb,0x49,0xd2,0x4a,0x29,0x3b,0x57,0x42,0x65,0x1c,0x94,0xa9,0x1b,0x8f,
-  0xc5,0x85,0xf6,0x2e,0x10,0x2b,0x64,0x6f,0x5c,0xe9,0xfb,0xd9,0xbb,0x95,0x47,0x8a,
-  0xe5,0x09,0xbd,0xb5,0x80,0x13,0x2d,0x8b,0x24,0x71,0xd0,0xb3,0x82,0x8b,0x09,0x49,
-  0x9d,0x24,0x01,0xe8,0x97,0x69,0xc0,0x77,0xc4,0x87,0x56,0x7a,0xa6,0x86,0x94,0xe8,
-  0x3d,0x5c,0x44,0x12,0x29,0xe1,0xd9,0x6d,0x51,0x94,0xaa,0x57,0x86,0x58,0x05,0xa4,
-  0x6b,0xbe,0x36,0xef,0xcc,0x9b,0x13,0xb9,0x53,0x2e,0x77,0x14,0xec,0x94,0xb0,0xbd,
-  0xb5,0x77,0xb0,0xb7,0xd8,0x5d,0x9b,0xe8,0x37,0x17,0xc1,0x1c,0x3b,0x65,0x8f,0xf4,
-  0xec,0x46,0xb8,0x3a,0xba,0xb8,0x12,0xa9,0xa9,0x38,0xce,0xfc,0x3f,0xd1,0xde,0x96,
-  0xc1,0x19,0xc1,0x69,0x6c,0x94,0x82,0x0d,0xc0,0xae,0xbd,0x81,0x14,0x75,0x41,0x4a,
-  0xb9,0xb3,0x38,0x14,0x08,0xd4,0xa1,0x63,0xd6,0x6b,0x45,0xc6,0xbb,0x19,0x82,0x8d,
-  0xa7,0xe3,0xe2,0x2a,0xea,0xb1,0x3f,0x88,0x8b,0xab,0xca,0xc4,0xea,0xf6,0xec,0x22,
-  0x26,0x93,0xd0,0x16,0x14,0xde,0xae,0x12,0xd5,0xab,0x68,0x7c,0x72,0x1f,0x71,0xd3,
-  0x76,0x58,0xfe,0x1b,0xfa,0xc6,0x04,0xe0,0x28,0xf3,0x47,0xeb,0xe3,0x64,0x77,0xb1,
-  0x18,0x71,0x37,0x5e,0x0a,0xf1,0x4a,0x3a,0xd5,0xe8,0x7b,0xf6,0x01,0xd1,0x23,0x5f,
-  0x23,0x54,0x2e,0x54,0x80,0xac,0x52,0xc6,0x42,0xb9,0x26,0xd2,0x08,0xb0,0xae,0x01,
-  0x47,0x33,0xdf,0x82,0xe3,0x8f,0xf4,0x1e,0x0d,0x01,0x6f,0x1f,0x59,0xb4,0xf5,0x01,
-  0xe2,0x22,0x82,0x8b,0xd9,0xed,0x32,0x32,0xbf,0xf7,0x0e,0x28,0xb9,0x3e,0x4d,0x71,
-  0x87,0xbe,0xdf,0x4e,0xad,0x2c,0x30,0xf2,0x6c,0xb8,0xc0,0x03,0x60,0x8e,0xd8,0xda,
-  0x18,0xc6,0x6b,0x33,0xf6,0x03,0x06,0xc7,0x10,0x80,0x40,0x78,0x36,0x5b,0x13,0xd9,
-  0xfc,0x16,0x44,0xff,0x01,0x17,0x05,0x67,0x30,0xfa,0x02,0x00,0x00,
+  0x1f,0x8b,0x08,0x00,0x00,0x00,0x00,0x00,0x02,0xff,0x75,0x52,0x47,0x77,0xdb,0x30,
+  0x0c,0xfe,0x2b,0x6c,0xa6,0xe8,0xed,0xec,0x44,0xa2,0x3b,0xf4,0x7a,0xea,0xde,0x67,
+  0x9a,0x82,0x2c,0xbe,0xd2,0x80,0x1e,0x04,0x59,0x59,0xfa,0xef,0x8d,0x57,0x77,0x70,
+  0xc1,0xde,0x5f,0xf2,0x24,0x23,0x27,0x37,0x25,0xa8,0x42,0xe6,0x61,0x92,0xcc,0x41,
+  0xac,0x72,0x85,0xe5,0x0a,0xc4,0xd4,0x92,0xf7,0x2f,0x36,0x36,0xb4,0x73,0x30,0x0b,
+  0x0f,0x4d,0x49,0x2c,0xca,0x11,0x0a,0xa0,0x98,0x9d,0xc6,0x67,0x52,0x98,0x0c,0x16,
+  0xde,0x41,0x7f,0xa5,0xf4,0x3c,0x7a,0xf1,0x36,0xf4,0x2b,0x67,0x03,0x98,0xf1,0xce,
+  0x24,0x11,0x2f,0x01,0x26,0x6f,0xa0,0x2a,0x52,0x62,0x50,0xdf,0x60,0x9a,0x12,0xe6,
+  0x7e,0x96,0x0c,0xd7,0x9e,0x64,0x4a,0xd9,0xcd,0xe4,0x35,0xd9,0xcc,0xe3,0x4c,0xfd,
+  0x1b,0x77,0x50,0x40,0x08,0xbe,0x8c,0x93,0xca,0xb1,0x2f,0x65,0x12,0xe5,0x35,0x3a,
+  0xf1,0x84,0x91,0xbe,0x5b,0x58,0x56,0x68,0x46,0xf1,0xd6,0xa4,0xc2,0x43,0x99,0x8d,
+  0x3d,0x35,0x8d,0xc7,0x8c,0x9a,0xc1,0xf3,0x29,0xb1,0xa4,0x84,0xc2,0x14,0x02,0x70,
+  0xcf,0x99,0xf4,0xe0,0x00,0xa1,0x51,0x69,0xa4,0x7b,0x62,0xdc,0xc1,0x41,0x05,0xf2,
+  0xd9,0xcf,0x81,0x6a,0xf9,0xbd,0xb8,0x1b,0xd8,0x65,0x66,0xa4,0xdb,0xde,0xe5,0xe8,
+  0x81,0x74,0x9c,0x83,0xb8,0x22,0xda,0x19,0xd6,0xfe,0xe9,0xc2,0x9c,0x64,0xe3,0x13,
+  0x0b,0x27,0x19,0x1c,0x1f,0x9d,0x5d,0x9c,0x8d,0x4e,0x77,0x7a,0xee,0xe9,0x5d,0xe5,
+  0x67,0x68,0xc3,0x95,0x1b,0xac,0x85,0xf6,0xea,0xae,0xd5,0x03,0x29,0x00,0x7f,0x15,
+  0x66,0x7d,0xe7,0xf3,0x88,0x07,0xf4,0x5d,0x33,0x48,0xcd,0xa8,0x78,0x20,0x70,0x2d,
+  0x91,0x8e,0x57,0xf6,0x4a,0xac,0xd4,0x95,0x31,0xe6,0x64,0x74,0xa9,0xef,0x02,0x39,
+  0xbb,0x4c,0x1b,0x30,0xac,0x77,0x8b,0x37,0x49,0x58,0x87,0xd0,0x4a,0xc1,0xd4,0xa8,
+  0x97,0xcc,0xc4,0xd1,0x8e,0xb0,0xc5,0x2a,0x07,0x56,0xb9,0xf5,0x01,0xb2,0x1d,0xfd,
+  0x4f,0xeb,0x72,0xd5,0x5a,0xb4,0x0b,0x60,0x79,0xbb,0xb1,0xac,0xfa,0x96,0xc6,0x98,
+  0x65,0xc9,0xcd,0x4c,0x71,0x46,0xae,0x9e,0x03,0xca,0x80,0x4a,0xc0,0x48,0xff,0xd2,
+  0x1b,0xf6,0x02,0x51,0xf9,0x9b,0xc5,0x05,0xaa,0x60,0x79,0xa5,0x9f,0x7d,0xe0,0xf1,
+  0x3e,0xdd,0x2e,0x26,0xc7,0xfa,0xb7,0x83,0x2f,0xb7,0xea,0x9d,0x8e,0x46,0x1d,0xd4,
+  0x31,0x84,0x0a,0xd4,0xcf,0xba,0x4b,0x5c,0xac,0x2e,0x93,0x6e,0xf1,0xf6,0x05,0xed,
+  0x34,0x80,0x12,0x5a,0xfd,0xf9,0x17,0x44,0xae,0xd4,0x4e,0x17,0xba,0x3b,0x03,0xf5,
+  0x11,0x56,0x0e,0x21,0xc5,0x20,0x7c,0x33,0xd8,0x69,0x75,0xbb,0x3e,0x5b,0xab,0x23,
+  0x9d,0x0c,0x37,0x10,0xfa,0x01,0x0f,0x69,0xb6,0x3f,0xf8,0x02,0x00,0x00,
 };
 
 const uint8_t WEBCONFIG_HTML_GZ[] PROGMEM = {
diff --git a/test/test_webconfig_gzip.py b/test/test_webconfig_gzip.py
index 397273cc..f2379ad2 100644
--- a/test/test_webconfig_gzip.py
+++ b/test/test_webconfig_gzip.py
@@ -52,6 +52,13 @@ class WebConfigGzipTest(unittest.TestCase):
         for page in (ROOT / "webui/pages").glob("*.html"):
             self.assertEqual(gzip.decompress(blobs["MESH_HTML_" + page.stem.upper()]), page.read_bytes())
 
+    def test_loader_matches_legacy_android_browser_syntax(self):
+        blobs = arrays((ROOT / "src/helpers/esp32/WebConfigHtml.h").read_text())
+        loader = gzip.decompress(blobs["WEBCONFIG_HTML_LOADER"]).decode()
+        script = loader.split("<script>", 1)[1].split("</script>", 1)[0]
+        self.assertNotIn("=>", script)
+        self.assertNotRegex(script, r"\b(?:async|await|let|const)\b")
+
     def test_gzip_binding_uses_1000_iterations_without_changing_raw_ota_default(self):
         with mock.patch.object(zopfli_compress._gzip, "compress",
                                return_value=gzip.compress(b"page", mtime=0)) as compress: