diff --git a/.gitignore b/.gitignore
index 715a9758c..88ab148b2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
 /libretro-super
 .DS_Store
+node_modules
+pnpm-lock.yaml
+package-lock.json
\ No newline at end of file
diff --git a/package.json b/package.json
new file mode 100644
index 000000000..bbaab38f0
--- /dev/null
+++ b/package.json
@@ -0,0 +1,11 @@
+{
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "check-duplicate": "node scripts/check-duplicate.js"
+  },
+  "devDependencies": {
+    "@retrobrainz/dat": "^1.0.1",
+    "chalk": "^5.6.2"
+  }
+}
diff --git a/scripts/check-duplicate.js b/scripts/check-duplicate.js
new file mode 100644
index 000000000..3cb798d11
--- /dev/null
+++ b/scripts/check-duplicate.js
@@ -0,0 +1,30 @@
+import { parse } from "@retrobrainz/dat";
+import chalk from "chalk";
+import { glob, readFile } from "node:fs/promises";
+
+for await (const datFile of glob(["dat/**/*.dat", "metadat/**/*.dat"], { exclude: ["dat/DOS.dat"] })) {
+  console.log(datFile);
+  const datContent = await readFile(datFile, "utf8");
+  const dat = parse(datContent);
+  const crcSerialMap = {};
+  for (const game of dat) {
+    if (
+      game.$class !== "game" ||
+      game.$entries?.length !== 1 ||
+      game.$entries?.[0].$class !== "rom"
+    ) {
+      continue;
+    }
+    const crc = game.$entries?.[0].crc;
+    const serial = game.$entries?.[0].serial || game.serial;
+    // if both crc and serial are the same, mark as duplicate
+    const key = JSON.stringify({crc, serial});
+    crcSerialMap[key] = (crcSerialMap[key] || 0) + 1;
+  }
+  for (const [key, count] of Object.entries(crcSerialMap)) {
+    if (count > 1) {
+      const {crc, serial} = JSON.parse(key);
+      console.log(chalk.red(`    duplicate: crc(${crc}), serial(${serial}), count(${count})`));
+    }
+  }
+}