diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
new file mode 100644
index 0000000..c595972
--- /dev/null
+++ b/.github/workflows/check.yml
@@ -0,0 +1,19 @@
+name: Deno Check
+
+on:
+    push:
+        branches:
+            - main
+    pull_request:
+
+jobs:
+    deno-check:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v4
+            - name: Set up Deno
+              uses: denoland/setup-deno@v1
+            #   with:
+                    # deno-version: v1.x
+            - name: Run deno check
+              run: deno run -R -N -E check.ts
\ No newline at end of file
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..b943dbc
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,3 @@
+{
+    "deno.enable": true
+}
\ No newline at end of file
diff --git a/check.ts b/check.ts
new file mode 100644
index 0000000..539986d
--- /dev/null
+++ b/check.ts
@@ -0,0 +1,71 @@
+// Deno script to ensure the core mods are valid
+
+interface CoreModListing {
+  [version: string]: GameCoreMods;
+}
+
+interface GameCoreMods {
+  lastUpdated: string;
+  mods: CoreMod[];
+}
+
+interface CoreMod {
+  id: string;
+  version: string;
+  downloadLink: string;
+}
+
+
+function isValidTime(timeStr: string) {
+  // Use Date parsing to check for valid ISO 8601 timestamp
+  const d = new Date(timeStr);
+  return !isNaN(d.getTime());
+}
+
+function isValidSemver(version: string) {
+  // assert string is semver
+  return /^\d+\.\d+\.\d+$/.test(version);
+}
+
+async function isValidUrl(url: string) {
+  // assert string is a valid URL
+  try {
+    const res = await fetch(url, { method: "HEAD" });
+    if (!res.ok) return false;
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+const json: CoreModListing = JSON.parse(
+  await Deno.readTextFile("./core_mods.json")
+);
+
+delete json["$schema"]; // Remove schema reference if present
+
+// ensure all have valid time
+Object.entries(json).forEach(([version, coreMods]) => {
+  console.log(`Checking version ${version}`);
+  if (!isValidTime(coreMods.lastUpdated)) {
+    throw new Error(
+      `Invalid lastUpdated time for version ${version}: ${coreMods.lastUpdated}`
+    );
+  }
+
+  coreMods.mods.forEach(async (mod) => {
+    if (!isValidSemver(mod.version)) {
+      throw new Error(
+        `Invalid version for mod ${mod.id} in version ${version}: ${mod.version}`
+      );
+    }
+    const validURL = await isValidUrl(mod.downloadLink);
+    if (!validURL) {
+      throw new Error(
+        `Invalid download link for mod ${mod.id} in version ${version}: ${mod.downloadLink}`
+      );
+    }
+    // Green color for valid mods using "colorette"
+    console.log(`%cMod ${mod.id} is valid`, "color: green");
+  });
+});