diff --git a/lib/ads/formats.ts b/lib/ads/formats.ts
index 391c896a..38593b4b 100644
--- a/lib/ads/formats.ts
+++ b/lib/ads/formats.ts
@@ -19,7 +19,11 @@ export const AD_FORMAT_IDS = AD_FORMATS.map((f) => f.id) as AdFormatId[];
 // embed for and install. A subset of AD_FORMATS that grows as each size is
 // surfaced (one PR per size). Keep the medium rectangle first: it's the safe
 // default the auto-installer falls back to.
-export const PUBLISHER_FORMAT_IDS: AdFormatId[] = ["banner_300x250", "banner_728x90"];
+export const PUBLISHER_FORMAT_IDS: AdFormatId[] = [
+  "banner_300x250",
+  "banner_728x90",
+  "banner_320x50",
+];
 
 export function formatSpec(id: AdFormatId) {
   return AD_FORMATS.find((f) => f.id === id) ?? AD_FORMATS[0];