---
name: "up.Preview.prototype.revalidating"
area: "API"
kind: "Property"
parent: "up.Preview class"
visibility: "experimental"
url: "https://unpoly.com/api/up.Preview.prototype.revalidating"
---
<nav aria-label="Unpoly docs">[All docs](https://unpoly.com/index.md) · [up.Preview class](https://unpoly.com/api/up.Preview.md)</nav>

# up.Preview.prototype.revalidating

**This feature is experimental**. Please [share](https://github.com/unpoly/unpoly/discussions) your experiences so we know what to keep or change.

Whether the previewed render pass is a [revalidation of an expired cache entry](https://unpoly.com/learn/caching.md#revalidation).

Cache revalidation is only previewed when an [`[up-revalidate-preview]`](https://unpoly.com/api/up-follow.md#up-revalidate-preview) attribute is set or when a [`{ revalidatePreview: true }`](https://unpoly.com/api/up.render.md#options.revalidatePreview) render option is passed.

When revalidating, the preview will be called _after_ the expired content has been rendered from the cache.

---

## Return value {#return-value}

Whether the preview is shown while revalidating.

Type: boolean