diff --git a/dwds/debug_extension_mv3/tool/build_extension.dart b/dwds/debug_extension_mv3/tool/build_extension.dart
new file mode 100644
index 000000000..4ed884ed9
--- /dev/null
+++ b/dwds/debug_extension_mv3/tool/build_extension.dart
@@ -0,0 +1,91 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// INSTRUCTIONS:
+
+// Builds the unminifed dart2js extension (see DDC issue:
+// see DDC issue: https://github.com/dart-lang/sdk/issues/49869).
+
+// Run from the extension root directory:
+//    - For dev: dart run tool/build_extension.dart
+//    - For prod: dart run tool/build_extension.dart prod
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:args/args.dart';
+import 'package:path/path.dart' as p;
+
+const _prodFlag = 'prod';
+
+void main(List<String> arguments) async {
+  final parser = ArgParser()
+    ..addFlag(_prodFlag, negatable: true, defaultsTo: false);
+  final argResults = parser.parse(arguments);
+
+  exitCode = await run(isProd: argResults[_prodFlag] as bool);
+  if (exitCode != 0) {
+    _logWarning('Run terminated unexpectedly with exit code: $exitCode');
+  }
+}
+
+Future<int> run({required bool isProd}) async {
+  _logInfo('Building extension for ${isProd ? 'prod' : 'dev'}');
+  _logInfo('Compiling extension with dart2js to /compiled directory');
+  final compileStep = await Process.start(
+    'dart',
+    ['run', 'build_runner', 'build', 'web', '--output', 'build', '--release'],
+  );
+  final compileExitCode = await _handleProcess(compileStep);
+  // Terminate early if compilation failed:
+  if (compileExitCode != 0) {
+    return compileExitCode;
+  }
+  _logInfo('Updating manifest.json in /compiled directory.');
+  final updateStep = await Process.start(
+    'dart',
+    [p.join('tool', 'update_dev_files.dart')],
+  );
+  final updateExitCode = await _handleProcess(updateStep);
+  // Return exit code (0 indicates success):
+  return updateExitCode;
+}
+
+Future<int> _handleProcess(Process process) async {
+  _handleOutput(process.stdout, isStdout: true);
+  _handleOutput(process.stderr, isStdout: false);
+  return process.exitCode;
+}
+
+void _handleOutput(Stream<List<int>> output, {bool isStdout = true}) {
+  output
+      .transform(utf8.decoder)
+      .transform(const LineSplitter())
+      .listen((line) => _handleOutputLine(line, isStdout: isStdout));
+}
+
+void _handleOutputLine(String line, {bool isStdout = true}) {
+  // Skip empty lines:
+  if (line.isEmpty) return;
+  // Log any unexpected errors and throw:
+  final outputName = isStdout ? 'stdout' : 'stderr';
+  if (line.toUpperCase().contains('SEVERE') ||
+      line.toUpperCase().contains('ERROR')) {
+    final error = 'Unexpected error in $outputName: $line';
+    _logWarning(error);
+    throw Exception(error);
+  }
+  // Log message to the terminal:
+  final message = '$outputName: $line';
+  isStdout ? _logInfo(message) : _logWarning(message);
+}
+
+void _logInfo(String message) {
+  stdout.writeln(message);
+}
+
+void _logWarning(String warning) {
+  stderr.writeln(warning);
+}
diff --git a/dwds/debug_extension_mv3/tool/build_extension.sh b/dwds/debug_extension_mv3/tool/build_extension.sh
deleted file mode 100755
index 9df8f4fa9..000000000
--- a/dwds/debug_extension_mv3/tool/build_extension.sh
+++ /dev/null
@@ -1,33 +0,0 @@
-#!/bin/bash
-
-# Copyright 2022 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.
-
-# INSTRUCTIONS:
-
-# Builds the unminifed dart2js app (see DDC issue: https://github.com/dart-lang/sdk/issues/49869):
-# ./tool/build_extension.sh
-
-
-prod="false"
-
-case "$1" in
-    prod)
-        prod="true"
-        shift;;
-esac
-
-echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
-echo "Building dart2js-compiled extension to /compiled directory."
-echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
-dart run build_runner build web --output build --release
-
-if [ $prod == true ]; then
-    exit 1
-fi
-
-echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
-echo "Updating manifest.json in /compiled directory."
-echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
-dart tool/update_dev_files.dart
diff --git a/dwds/test/puppeteer/test_utils.dart b/dwds/test/puppeteer/test_utils.dart
index 5ef0719c9..0c8c93e98 100644
--- a/dwds/test/puppeteer/test_utils.dart
+++ b/dwds/test/puppeteer/test_utils.dart
@@ -13,10 +13,9 @@ import '../fixtures/utilities.dart';
 
 Future<String> buildDebugExtension() async {
   final extensionDir = absolutePath(pathFromDwds: 'debug_extension_mv3');
-  // TODO(elliette): This doesn't work on Windows, see https://github.com/dart-lang/webdev/issues/1724.
   await Process.run(
-    p.join('tool', 'build_extension.sh'),
-    [],
+    'dart',
+    [p.join('tool', 'build_extension.dart')],
     workingDirectory: extensionDir,
   );
   return p.join(extensionDir, 'compiled');