---
description: We performed a one-time update to disable preview URLs on Workers with workers.dev disabled to require an explicit opt-in.
title: Preview URLs now default to opt-in
image: https://developers.cloudflare.com/changelog/post/2025-09-17-update-preview-url-setting/og.png?v=9a622928d8bde8c3
---

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September 17, 2025

## Preview URLs now default to opt-in

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

Copy as Markdown| [View as Markdown](https://developers.cloudflare.com/changelog/post/2025-09-17-update-preview-url-setting/index.md)| [Agent setup](https://developers.cloudflare.com/agent-setup/)

To prevent the accidental exposure of applications, we've updated how [Worker preview URLs](https://developers.cloudflare.com/workers/versions-and-deployments/version-urls/) (`<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/versions-and-deployments/version-urls/#enable-or-disable-version-urls) 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.

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

```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.

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```