diff --git a/src/utils/standard-site.js b/src/utils/standard-site.js
deleted file mode 100644
index 217c1ff6..00000000
--- a/src/utils/standard-site.js
+++ /dev/null
@@ -1,42 +0,0 @@
-const STANDARD_SITE_DOCUMENT_COLLECTION = 'site.standard.document';
-
-export function isStandardSiteDocumentRecord(record) {
-  if (!record) return false;
-
-  if (typeof record === 'string') {
-    return record.includes(STANDARD_SITE_DOCUMENT_COLLECTION);
-  }
-
-  if (typeof record !== 'object') return false;
-
-  const uri = record.uri || record.record?.uri;
-  const collection = record.collection || record.record?.collection;
-  const type = record.$type || record.record?.$type;
-
-  return [uri, collection, type].some((value) =>
-    String(value || '').includes(STANDARD_SITE_DOCUMENT_COLLECTION),
-  );
-}
-
-export function isLeafletUrl(url) {
-  try {
-    const { hostname } = new URL(url);
-    return (
-      hostname === 'leaflet.pub' ||
-      hostname.endsWith('.leaflet.pub') ||
-      hostname.startsWith('leaflet.')
-    );
-  } catch {
-    return false;
-  }
-}
-
-export function canReadCardInline(card) {
-  if (!card?.url) return false;
-
-  return (
-    isLeafletUrl(card.url) ||
-    isStandardSiteDocumentRecord(card.associatedRecord) ||
-    isStandardSiteDocumentRecord(card.associated_record)
-  );
-}
diff --git a/src/utils/standard-site.ts b/src/utils/standard-site.ts
new file mode 100644
index 00000000..119e89f6
--- /dev/null
+++ b/src/utils/standard-site.ts
@@ -0,0 +1,79 @@
+const STANDARD_SITE_DOCUMENT_COLLECTION = 'site.standard.document';
+
+interface StandardSiteRecordFields {
+  $type?: unknown;
+  collection?: unknown;
+  uri?: unknown;
+}
+
+interface StandardSiteDocumentCandidate extends StandardSiteRecordFields {
+  record?: StandardSiteRecordFields;
+}
+
+interface CardCandidate {
+  associated_record?: unknown;
+  associatedRecord?: unknown;
+  url?: string;
+}
+
+function hasStandardSiteDocumentCollection(value: unknown): boolean {
+  return (
+    typeof value === 'string' &&
+    value.includes(STANDARD_SITE_DOCUMENT_COLLECTION)
+  );
+}
+
+function isObject(value: unknown): value is object {
+  return typeof value === 'object' && Object(value) === value;
+}
+
+function isStandardSiteDocumentRecord(record: unknown): boolean {
+  if (typeof record === 'string') {
+    return record.includes(STANDARD_SITE_DOCUMENT_COLLECTION);
+  }
+
+  if (!isObject(record)) {
+    return false;
+  }
+
+  const candidate = record as StandardSiteDocumentCandidate;
+  const uri = candidate.uri || candidate.record?.uri;
+  const collection = candidate.collection || candidate.record?.collection;
+  const type = candidate.$type || candidate.record?.$type;
+
+  return [uri, collection, type].some((value) =>
+    hasStandardSiteDocumentCollection(value),
+  );
+}
+
+function isLeafletUrl(url: string): boolean {
+  try {
+    const { hostname } = new URL(url);
+    return (
+      hostname === 'leaflet.pub' ||
+      hostname.endsWith('.leaflet.pub') ||
+      hostname.startsWith('leaflet.')
+    );
+  } catch {
+    return false;
+  }
+}
+
+function canReadCardInline(card: unknown): boolean {
+  if (!isObject(card)) {
+    return false;
+  }
+
+  const candidate = card as CardCandidate;
+  if (typeof candidate.url !== 'string' || candidate.url === '') {
+    return false;
+  }
+
+  return (
+    isLeafletUrl(candidate.url) ||
+    isStandardSiteDocumentRecord(candidate.associatedRecord) ||
+    isStandardSiteDocumentRecord(candidate.associated_record)
+  );
+}
+
+export { canReadCardInline, isLeafletUrl, isStandardSiteDocumentRecord };
diff --git a/tests/atproto-standard-site.spec.js b/tests/atproto-standard-site.spec.js
index f7d4b5bc..317afd80 100644
--- a/tests/atproto-standard-site.spec.js
+++ b/tests/atproto-standard-site.spec.js
@@ -5,7 +5,7 @@ import {
   canReadCardInline,
   isLeafletUrl,
   isStandardSiteDocumentRecord,
-} from '../src/utils/standard-site.js';
+} from '../src/utils/standard-site.ts';
 
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