diff --git a/src/utils/file.ts b/src/utils/file.ts
new file mode 100644
index 0000000..a3200ac
--- /dev/null
+++ b/src/utils/file.ts
@@ -0,0 +1,11 @@
+/**
+ * Returns the file extension
+ *
+ * @param {string} filename - The filename
+ * @return {string} - the file extension
+ */
+export function getFileExtension(filename: string): string {
+  const lastDot = filename.lastIndexOf('.');
+  if (lastDot <= 0) return ''; // No extension
+  return filename.slice(lastDot + 1).toLowerCase();
+}