---
title: Preview URLs now default to opt-in
description: We performed a one-time update to disable preview URLs on Workers with workers.dev disabled to require an explicit opt-in.
image: https://developers.cloudflare.com/changelog-preview.png
---

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## Preview URLs now default to opt-in

Sep 17, 2025 

[ Workers ](https://developers.cloudflare.com/workers/) 

To prevent the accidental exposure of applications, we've updated how [Worker preview URLs](https://developers.cloudflare.com/workers/configuration/previews/) (`<PREVIEW>-<WORKER_NAME>.<SUBDOMAIN>.workers.dev`) are handled. We made this change to ensure preview URLs are only active when intentionally configured, improving the default security posture of your Workers.

#### One-Time Update for Workers with workers.dev Disabled

We performed a one-time update to disable preview URLs for existing Workers where the [workers.dev subdomain](https://developers.cloudflare.com/workers/configuration/routing/workers-dev/) was also disabled.

Because preview URLs were historically enabled by default, users who had intentionally disabled their workers.dev route may not have realized their Worker was still accessible at a separate preview URL. This update was performed to ensure that using a preview URL is always an intentional, opt-in choice.

If your Worker was affected, its preview URL (`<PREVIEW>-<WORKER_NAME>.<SUBDOMAIN>.workers.dev`) will now direct to an informational page explaining this change.

**How to Re-enable Your Preview URL**

If your preview URL was disabled, you can re-enable it [via the Cloudflare dashboard](https://developers.cloudflare.com/workers/configuration/previews/#toggle-preview-urls-enable-or-disable) by navigating to your Worker's Settings page and toggling on the Preview URL.

Alternatively, you can use Wrangler by adding the `preview_urls = true` setting to your Wrangler file and redeploying the Worker.

* [  wrangler.jsonc ](#tab-panel-2729)
* [  wrangler.toml ](#tab-panel-2730)

**JSONC**

```jsonc
{
  "preview_urls": true
}
```

**TOML**

```toml
preview_urls = true
```

**Note:** You can set `preview_urls = true` with any Wrangler version that supports the preview URL flag (v3.91.0+). However, we recommend updating to v4.34.0 or newer, as this version defaults `preview_urls` to false, ensuring preview URLs are always enabled by explicit choice.

```json
{"@context":"https://schema.org","@type":"BlogPosting","@id":"https://developers.cloudflare.com/changelog/post/2025-09-17-update-preview-url-setting/#page","headline":"Preview URLs now default to opt-in · Changelog","description":"We performed a one-time update to disable preview URLs on Workers with workers.dev disabled to require an explicit opt-in.","url":"https://developers.cloudflare.com/changelog/post/2025-09-17-update-preview-url-setting/","inLanguage":"en","image":"https://developers.cloudflare.com/changelog-preview.png","dateModified":"2025-09-17","datePublished":"2025-09-17","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}}
```