diff --git a/lib/ads/house.ts b/lib/ads/house.ts
new file mode 100644
index 00000000..50472bf7
--- /dev/null
+++ b/lib/ads/house.ts
@@ -0,0 +1,96 @@
+import crypto from "node:crypto";
+import { env } from "@/lib/env";
+import { formatSpec, type AdCreative, type AdFormatId } from "./creative";
+import type { Fill } from "./serve";
+
+// Default "house" ad for the CrawlProof Ad Network. Shown when a slot has no
+// eligible paid campaign, so a publisher's unit is never blank. Uses default
+// AI-generated promo artwork (public/ads/house/*) with an overlaid pitch that
+// links back to CrawlProof. House ads are not metered or billed.
+
+const HOUSE = {
+ headline: "Your ad here",
+ body: "Crypto pay-per-click ads for indie sites — no middlemen.",
+ cta: "Advertise →",
+} as const;
+
+function imageUrlFor(format: AdFormatId): string {
+ const rect = format === "banner_300x250";
+ return `${env.siteUrl}/ads/house/${rect ? "promo-rect" : "promo-wide"}.webp`;
+}
+
+function esc(s: string): string {
+ return s.replace(/&/g, "&").replace(//g, ">").replace(/"/g, """);
+}
+
+export function renderHouseAdHtml(format: AdFormatId, clickUrl: string): string {
+ const { w, h } = formatSpec(format);
+ const img = imageUrlFor(format);
+ const isMobile = format === "banner_320x50";
+ const isRect = format === "banner_300x250";
+ const row = !isRect; // leaderboard + mobile are horizontal
+
+ const label = `CrawlProof Ads`;
+ const headline = `${esc(HOUSE.headline)}
`;
+ const body = isMobile
+ ? ""
+ : `${esc(HOUSE.body)}
`;
+ const cta = `${esc(HOUSE.cta)}`;
+
+ const content = row
+ ? `
+
${headline}${body}
+
${cta}
+
+
${headline}${body}
+
${cta}
+