diff --git a/modules/worldAdsIdSystem.js b/modules/worldAdsIdSystem.js
new file mode 100644
index 00000000000..c42de2c63f3
--- /dev/null
+++ b/modules/worldAdsIdSystem.js
@@ -0,0 +1,82 @@
+/**
+ * This module adds World Ads (World ID verified identity) to the User ID module.
+ * It emits the verified World ID credential that the World Ads drop-in stored
+ * first-party (after a World ID ceremony) as a `world.org` EID, so it rides the
+ * bid request and an operator can verify-before-trust.
+ * @module modules/worldAdsIdSystem
+ * @requires module:modules/userId
+ */
+import { submodule } from '../src/hook.js';
+import { getStorageManager } from '../src/storageManager.js';
+import { MODULE_TYPE_UID } from '../src/activities/modules.js';
+
+const MODULE_NAME = 'worldAds';
+const EID_SOURCE = 'world.org';
+// Keys written first-party by the World Ads drop-in (embed.js) after a verify:
+// the RP-scoped nullifier, and the full World ID verify response (the proof).
+const NULLIFIER_KEY = '_worldads_nf';
+const PROOF_KEY = '_worldads_proof';
+
+export const storage = getStorageManager({ moduleType: MODULE_TYPE_UID, moduleName: MODULE_NAME });
+
+function readNullifier() {
+  let v;
+  try { v = storage.getDataFromLocalStorage(NULLIFIER_KEY); } catch (e) {}
+  if (!v) {
+    try { v = storage.getCookie(NULLIFIER_KEY); } catch (e) {}
+  }
+  return v || null;
+}
+
+function readProof() {
+  try {
+    const s = storage.getDataFromLocalStorage(PROOF_KEY);
+    return s ? JSON.parse(s) : null;
+  } catch (e) {
+    return null;
+  }
+}
+
+/** @type {Submodule} */
+export const worldAdsIdSubmodule = {
+  name: MODULE_NAME,
+
+  /**
+   * @param {{nullifier: string, proof: ?object}} value
+   * @returns {{worldAds: {nullifier: string, proof: ?object}}|undefined}
+   */
+  decode(value) {
+    return value && value.nullifier ? { [MODULE_NAME]: value } : undefined;
+  },
+
+  /**
+   * Read the verified World ID credential the drop-in stored first-party.
+   * No params/storage config needed — the drop-in owns the storage.
+   * @returns {{id: {nullifier: string, proof: ?object}}|undefined}
+   */
+  getId() {
+    const nullifier = readNullifier();
+    if (!nullifier) return undefined;
+    return { id: { nullifier, proof: readProof() } };
+  },
+
+  eids: {
+    [MODULE_NAME]: {
+      source: EID_SOURCE,
+      atype: 3,
+      getValue(data) {
+        return data.nullifier;
+      },
+      getUidExt(data) {
+        const ext = { stype: 'other' };
+        // Carry the full verify response so an operator can verify-before-trust,
+        // rather than trust a bare nullifier. (Production: this should be a sealed
+        // token rather than the raw proof; see worldAdsIdSystem.md.)
+        if (data.proof) ext.proof = data.proof;
+        return ext;
+      },
+    },
+  },
+};
+
+submodule('userId', worldAdsIdSubmodule);
diff --git a/modules/worldAdsIdSystem.md b/modules/worldAdsIdSystem.md
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+++ b/modules/worldAdsIdSystem.md
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+# World Ads ID System
+
+The World Ads ID submodule emits a **World ID** verified-identity credential as a
+`world.org` EID. The [World Ads drop-in](https://worldads-signer.scope3.workers.dev/embed.js)
+runs the World ID ceremony and stores the result first-party (`_worldads_nf` +
+`_worldads_proof`); this submodule reads it and attaches it to the bid request so
+an operator can **verify-before-trust** the proof.
+
+## Emitted EID
+
+```json
+{
+  "source": "world.org",
+  "uids": [{
+    "id": "<rp-scoped nullifier>",
+    "atype": 3,
+    "ext": {
+      "stype": "other",
+      "proof": { "...": "the full World ID verify response (identifier, nullifier, proof, …)" }
+    }
+  }]
+}
+```
+
+`uids[0].id` is the nullifier (for matching/dedup); `uids[0].ext.proof` carries the
+verifiable credential. A consumer should verify the proof and use the **verified**
+nullifier for any frequency/eligibility key, treating `id` as a hint.
+
+## Configuration
+
+No params or storage config — the drop-in owns the storage:
+
+```js
+pbjs.setConfig({
+  userSync: {
+    userIds: [{
+      name: 'worldAds'
+    }]
+  }
+});
+```
+
+Build with:
+
+```
+gulp build --modules=userId,worldAdsIdSystem
+```
+
+## Notes
+
+- Requires the [World Ads drop-in](https://worldads-signer.scope3.workers.dev/embed.js)
+  on the page to run the verify and store the credential.
+- **Production hardening:** `ext.proof` currently carries the raw verify response.
+  For an open bidstream it should be a token **sealed/encrypted to the operator's
+  key** (only the operator can open it), not the raw proof — large, and broadcasts
+  the credential. The raw form is appropriate for a controlled, operator-only path.