diff --git a/build_config/build_config.bzl b/build_config/build_config.bzl
index 3deb9d1..5960d2a 100644
--- a/build_config/build_config.bzl
+++ b/build_config/build_config.bzl
@@ -20,16 +20,8 @@
     "//conditions:default": [],
 })
 
-_icuuc_deps = select({
-    "//build_config:with_system_icu": [],
-
-    # If we don't link against system ICU library, we must provide "@org_unicode_icuuc//:common".
-    "//conditions:default": ["@org_unicode_icuuc//:common"],
-})
-
 build_config = struct(
     default_copts = _default_copts,
     url_linkopts = _url_linkopts,
     strings_hdrs = _strings_hdrs,
-    icuuc_deps = _icuuc_deps,
 )
diff --git a/copy.bara.sky b/copy.bara.sky
index 6bf0772..0f78461 100644
--- a/copy.bara.sky
+++ b/copy.bara.sky
@@ -37,10 +37,11 @@
         "build/buildflag.h",
         "url/*.cc",
         "url/*.h",
+        "url/url_idna_icu_alternatives_ios.mm",
         "url/third_party/mozilla/**",
     ],
     exclude = [
-        "url/url_idna_icu_alternatives*",
+        "url/url_idna_icu_alternatives_android.cc",
     ],
 )
 
@@ -93,6 +94,10 @@
     # Use Abseil at upstream-recommended paths.
     core.replace("third_party/abseil-cpp/absl", "absl"),
 
+    # iOS version of url_idna is ASCII-only, but it uses .mm extension; rename
+    # it to a .cc file.
+    core.move("url/url_idna_icu_alternatives_ios.mm", "url/url_idna_ascii_only.cc"),
+
     # Fix some Perfetto includes.
     core.replace("perfetto/tracing/traced_value_forward.h", "perfetto/tracing/traced_value.h"),
 
diff --git a/test/BUILD b/test/BUILD
index 16b1a42..b71bb78 100644
--- a/test/BUILD
+++ b/test/BUILD
@@ -4,9 +4,15 @@
 load("//build_config:build_config.bzl", "build_config")
 load("@rules_cc//cc:defs.bzl", "cc_test")
 
+idna_extra_defines = select({
+    "//build_config:with_system_icu": ["GOOGLEURL_SUPPORTS_IDNA"],
+    "//conditions:default": [],
+})
+
 cc_test(
     name = "basic_test",
     srcs = ["basic_test.cc"],
     copts = build_config.default_copts,
+    defines = idna_extra_defines,
     deps = ["//url"],
 )
diff --git a/test/basic_test.cc b/test/basic_test.cc
index f60df57..6253e25 100644
--- a/test/basic_test.cc
+++ b/test/basic_test.cc
@@ -29,7 +29,11 @@
 
   // Ensure ICU is functioning correctly.
   GURL idn_url("https://\xe5\x85\x89.example/");
+#ifdef GOOGLEURL_SUPPORTS_IDNA
   ASSERT_EQ(idn_url.spec(), "https://xn--54q.example/");
+#else
+  ASSERT_EQ(idn_url.is_valid(), false);
+#endif
 
   return 0;
 }
diff --git a/url/BUILD b/url/BUILD
index 24fd97e..c6b53ab 100644
--- a/url/BUILD
+++ b/url/BUILD
@@ -4,6 +4,11 @@
 load("//build_config:build_config.bzl", "build_config")
 load("@rules_cc//cc:defs.bzl", "cc_library")
 
+idna_src = select({
+    "//build_config:with_system_icu": ["url_idna_icu.cc"],
+    "//conditions:default": ["url_idna_ascii_only.cc"],
+})
+
 cc_library(
     name = "url",
     srcs = [
@@ -26,12 +31,11 @@
         "url_canon_stdstring.cc",
         "url_canon_stdurl.cc",
         "url_constants.cc",
-        "url_idna_icu.cc",
         "url_parse_file.cc",
         "url_parse_internal.h",
         "url_util.cc",
         "url_util_internal.h",
-    ],
+    ] + idna_src,
     hdrs = [
         "gurl.h",
         "third_party/mozilla/url_parse.h",
@@ -49,5 +53,5 @@
     deps = [
         "//base",
         "//polyfills",
-    ] + build_config.icuuc_deps,
+    ],
 )
diff --git a/url/url_idna_ascii_only.cc b/url/url_idna_ascii_only.cc
new file mode 100644
index 0000000..55e8459
--- /dev/null
+++ b/url/url_idna_ascii_only.cc
@@ -0,0 +1,28 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <string.h>
+
+#include <ostream>
+#include <string>
+
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "url/url_canon_internal.h"
+
+namespace url {
+
+// Only allow ASCII to avoid ICU dependency. Use NSString+IDN
+// to convert non-ASCII URL prior to passing to API.
+bool IDNToASCII(const char16_t* src, int src_len, CanonOutputW* output) {
+  if (gurl_base::IsStringASCII(gurl_base::StringPiece16(src, src_len))) {
+    output->Append(src, src_len);
+    return true;
+  }
+  GURL_DCHECK(false) << "IDN URL support is not available.";
+  return false;
+}
+
+}  // namespace url