diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index 570a8f1..893d621 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -36,7 +36,7 @@ Purpose: Provide just enough project context so an AI assistant can make correct
 ### 4. Testing Strategy
 * Unit tests in `test/unit/` mirror README examples & edge cases (list formats, depth, duplicates, charsets, null handling, custom hooks).
 * E2E tests in `test/e2e/` exercise higher‑level URI extensions.
-* Comparison tests (`test/comparison/`) ensure parity with the JS implementation via fixture JSON & a Node script; run `test/comparison/compare_outputs.sh` after semantic changes to core encode/decode logic.
+* Comparison tests (`test/comparison/`) ensure Dart VM and dart2js parity with the JS implementation via fixture JSON & a Node script; run `test/comparison/compare_outputs.sh` after semantic changes to core encode/decode logic.
 * When adding behavior, first add/modify a unit test replicating the JS `qs` behavior (consult upstream if uncertain), then adjust implementation.
 
 ### 5. Dev Workflow / Commands
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b80cce9..82f2654 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -237,16 +237,7 @@ jobs:
         run: pnpm install --frozen-lockfile
       - name: Run a comparison test between qs_dart and qs for JavaScript
         working-directory: test/comparison
-        run: |
-          set -e
-          node_output=$(node qs.js)
-          dart_output=$(dart run qs.dart)
-          if [ "$node_output" == "$dart_output" ]; then
-              echo "The outputs are identical."
-          else
-              echo "The outputs are different."
-              exit 1
-          fi
+        run: bash compare_outputs.sh
   ci_required:
     name: "CI Required"
     if: ${{ always() }}
diff --git a/test/comparison/compare_outputs.sh b/test/comparison/compare_outputs.sh
index ebe11b2..da73566 100755
--- a/test/comparison/compare_outputs.sh
+++ b/test/comparison/compare_outputs.sh
@@ -1,17 +1,33 @@
 #!/usr/bin/env bash
 
-# Get the directory of the script
-script_dir=$(dirname "$0")
-
-# Run the JavaScript and Dart scripts and save their outputs
-node_output=$(node "$script_dir/qs.js")
-dart_output=$(dart run "$script_dir/qs.dart")
-
-# Compare the outputs
-if [ "$node_output" == "$dart_output" ]; then
-    echo "The outputs are identical."
-    exit 0
-else
-    echo "The outputs are different."
+set -euo pipefail
+
+script_dir=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+tmp_dir=$(mktemp -d)
+trap 'rm -rf "$tmp_dir"' EXIT
+
+compare_outputs() {
+  local expected="$1"
+  local actual="$2"
+  local description="$3"
+
+  if ! diff -u "$expected" "$actual"; then
+    echo "$description outputs are different." >&2
     exit 1
-fi
+  fi
+}
+
+node "$script_dir/qs.js" > "$tmp_dir/node.out"
+dart run "$script_dir/qs.dart" > "$tmp_dir/dart_vm.out"
+
+test_cases_base64=$(base64 < "$script_dir/test_cases.json" | tr -d '\r\n')
+dart compile js -O2 \
+  -DQS_COMPARISON_TEST_CASES_BASE64="$test_cases_base64" \
+  "$script_dir/qs_dart2js.dart" \
+  -o "$tmp_dir/qs_dart2js.js"
+node "$tmp_dir/qs_dart2js.js" > "$tmp_dir/dart2js.out"
+
+compare_outputs "$tmp_dir/node.out" "$tmp_dir/dart_vm.out" "Node and Dart VM"
+compare_outputs "$tmp_dir/node.out" "$tmp_dir/dart2js.out" "Node and dart2js"
+
+echo "The Node, Dart VM, and dart2js outputs are identical."
diff --git a/test/comparison/comparison.dart b/test/comparison/comparison.dart
new file mode 100644
index 0000000..c04a2e9
--- /dev/null
+++ b/test/comparison/comparison.dart
@@ -0,0 +1,15 @@
+import 'dart:convert' show jsonDecode, jsonEncode;
+
+import 'package:qs_dart/qs_dart.dart' as qs;
+
+Iterable<String> buildComparisonLines(String testCasesJson) sync* {
+  final List<Map<String, dynamic>> e2eTestCases =
+      List.from(jsonDecode(testCasesJson));
+
+  for (final Map<String, dynamic> testCase in e2eTestCases) {
+    final String encoded = qs.encode(testCase['data']);
+    final Map decoded = qs.decode(testCase['encoded']);
+    yield 'Encoded: $encoded';
+    yield 'Decoded: ${jsonEncode(decoded)}';
+  }
+}
diff --git a/test/comparison/package.json b/test/comparison/package.json
index f6ebede..8ce423c 100644
--- a/test/comparison/package.json
+++ b/test/comparison/package.json
@@ -4,7 +4,7 @@
   "description": "A comparison of query string parsing libraries",
   "author": "Klemen Tusar",
   "license": "BSD-3-Clause",
-  "packageManager": "pnpm@11.1.3",
+  "packageManager": "pnpm@11.5.2",
   "dependencies": {
     "qs": "^6.15.2"
   }
diff --git a/test/comparison/qs.dart b/test/comparison/qs.dart
index 3650f66..97c6055 100644
--- a/test/comparison/qs.dart
+++ b/test/comparison/qs.dart
@@ -1,9 +1,9 @@
-import 'dart:convert' show jsonDecode, jsonEncode;
 import 'dart:io' show File, Platform, exitCode, stdout;
 
 import 'package:cli_script/cli_script.dart' show wrapMain;
 import 'package:path/path.dart' as p;
-import 'package:qs_dart/qs_dart.dart' as qs;
+
+import 'comparison.dart';
 
 void main() {
   wrapMain(() {
@@ -12,16 +12,9 @@ void main() {
     final String scriptDir = p.dirname(Platform.script.toFilePath());
     final File file = File(p.join(scriptDir, 'test_cases.json'));
     final String contents = file.readAsStringSync();
-    final List<Map<String, dynamic>> e2eTestCases =
-        List<Map<String, dynamic>>.from(
-      jsonDecode(contents),
-    );
 
-    for (final testCase in e2eTestCases) {
-      final String encoded = qs.encode(testCase['data']);
-      final Map decoded = qs.decode(testCase['encoded']);
-      stdout.writeln('Encoded: $encoded');
-      stdout.writeln('Decoded: ${jsonEncode(decoded)}');
+    for (final String line in buildComparisonLines(contents)) {
+      stdout.writeln(line);
     }
   });
 }
diff --git a/test/comparison/qs_dart2js.dart b/test/comparison/qs_dart2js.dart
new file mode 100644
index 0000000..90019ed
--- /dev/null
+++ b/test/comparison/qs_dart2js.dart
@@ -0,0 +1,17 @@
+import 'dart:convert' show base64Decode, utf8;
+
+import 'comparison.dart';
+
+void main() {
+  const String encodedTestCases =
+      String.fromEnvironment('QS_COMPARISON_TEST_CASES_BASE64');
+  if (encodedTestCases.isEmpty) {
+    throw StateError('Missing QS_COMPARISON_TEST_CASES_BASE64.');
+  }
+
+  final String testCasesJson = utf8.decode(base64Decode(encodedTestCases));
+  for (final String line in buildComparisonLines(testCasesJson)) {
+    // ignore: avoid_print
+    print(line);
+  }
+}