> ## Documentation Index
> Fetch the complete documentation index at: https://docs.encorekit.com/llms.txt
> Use this file to discover all available pages before exploring further.

# onStrictUnlockVerified()

> Subscribe to a strict-mode claim being confirmed by the advertiser's postback

Fires when the advertiser's postback confirms a claim. Applies only when
[`configure()`](/publishers/web/sdk-reference/configure#unlock-mode) set
`unlockMode: 'strict'`.

## Structure

```typescript theme={null}
Encore.onStrictUnlockVerified(
  callback: (transactionId: string) => void
): () => void;   // returns an unsubscribe function
```

| Parameter  | Type                              | Description                                         |
| ---------- | --------------------------------- | --------------------------------------------------- |
| `callback` | `(transactionId: string) => void` | Receives the transaction id of the confirmed claim. |

## When to use it

Subscribe when running in strict mode and you want to react to a confirmation that lands
after [`show()`](/publishers/web/sdk-reference/show) has resolved. The postback usually
arrives once the user is already at the advertiser, and sometimes after the page that made
the claim is gone, so no return value can carry it.

Register the callback immediately after `configure()`. A claim left pending by an earlier
page load is re-checked during SDK initialization, so a late subscription misses it.

```javascript theme={null}
Encore.configure({
  apiKey: 'pk_live_yourpublishablekey',
  unlockMode: 'strict',
});

const unsubscribe = Encore.onStrictUnlockVerified((transactionId) => {
  console.debug('claim verified', transactionId);
  void refreshEntitlementsFromYourBackend(transactionId);
});
```

## Behavior

| Aspect          | Behavior                                                                                                                                     |
| --------------- | -------------------------------------------------------------------------------------------------------------------------------------------- |
| Firing          | Once per verified claim, for both an in-session confirmation and one recovered on a later page load. The callback does not distinguish them. |
| Retries         | A claim that has not verified is re-checked on every return to the tab, for up to seven days.                                                |
| Payload         | The transaction id and nothing else. A recovered verification has no presentation left in scope to describe.                                 |
| Unsubscribing   | Call the returned function.                                                                                                                  |
| Optimistic mode | Never fires, since nothing is verified.                                                                                                      |

<Warning>
  This is a signal, not an authorization. It reports that Encore observed the advertiser's
  postback, and it is delivered by client-side code. Treat it as a prompt to re-read
  entitlements from your backend through Encore's server-side entitlements API, which is
  authoritative.
</Warning>

## Related

* [`configure()`](/publishers/web/sdk-reference/configure#unlock-mode): turning on strict mode.
* [`show()`](/publishers/web/sdk-reference/show): resolves `'claimed'` at handoff in both modes.