Update 2025-10-23-preview-url-default-behavior.mdx

Author: dinasaur404

src/content/changelog/workers/2025-10-23-preview-url-default-behavior.mdx

@@ -3,16 +3,32 @@ title: Workers Preview URL default behavior now matches your workers.dev setting
 description: If a Workers Preview URL setting is not explicitly configured, its default behavior will now match the setting of the workers.dev subdomain.
 date: 2025-10-23
 ---
-We have updated the default behavior for Cloudflare Workers [Preview URLs](/workers/configuration/previews/). Going forward, if a preview URL setting is not [explicitly configured](/workers/configuration/previews/#toggle-preview-urls-enable-or-disable) during deployment, its default behavior will automatically match the setting of your `[workers.dev` subdomain](/workers/configuration/routing/workers-dev/).
+We have updated the default behavior for Cloudflare Workers [Preview URLs](/workers/configuration/previews/). **Going forward, if a preview URL setting is not [explicitly configured](/workers/configuration/previews/#toggle-preview-urls-enable-or-disable) during deployment, its default behavior will automatically match the setting of your [`workers.dev` subdomain](/workers/configuration/routing/workers-dev/).**
 
 This change is intended to provide a more intuitive and secure experience by aligning your preview URL's default state with your `workers.dev` configuration to prevent cases where a preview URL might remain public even after you disabled your `workers.dev` route.
 
-Here is how the new default logic works:
+**What this means for you:**
+- **If neither setting is configured:** both the workers.dev route and the preview URL will default to enabled
+- **If your workers.dev route is enabled and no preview URL is set:** Preview URLs will default to enabled
+- **If your workers.dev route is disabled and no preview URL is set:** Preview URLs will default to disabled
 
-- If your `workers.dev` route is enabled (or not configured) and no preview URL is set, Preview URLs will default to enabled.
+You can override the default setting by explicitly enabling or disabling the preview URL in your Worker's configuration through the [API](/api/resources/workers/subresources/scripts/subresources/subdomain/), [Dashboard](/workers/configuration/previews/#from-the-dashboard), or [Wrangler](/workers/configuration/previews/#from-the-wrangler-configuration-file). 
 
-- If your `workers.dev` route is disabled and no preview URL is set, Preview URLs will default to disabled.
+**Wrangler Version Behavior**
+The default behavior depends on the version of Wrangler you are using. This new logic applies to the latest version. Here is a summary of the behavior across different versions:
+- Before v4.34.0: Preview URLs defaulted to enabled, regardless of the workers.dev setting.
+- v4.34.0 up to the latest version: Preview URLs defaulted to disabled, regardless of the workers.dev setting.
+- Latest version: Preview URLs now default to matching your workers.dev setting.
 
-You can override the default setting by explicitly enabling or disabling the preview URL in your Worker's configuration through the [API](/api/resources/workers/subresources/scripts/subresources/subdomain/), [Dashboard](/workers/configuration/previews/#from-the-dashboard), or [Wrangler](/workers/configuration/previews/#from-the-wrangler-configuration-file). This new logic applies when deploying with the latest version of Wrangler.
+**Why we’re making this change**
+In July, we introduced preview URLs to Workers, which let you preview code changes before deploying to production. This made disabling your Worker’s workers.dev URL an ambiguous action — the preview URL, served as a subdomain of `workers.dev` (ex: `preview-id-worker-name.account-name.workers.dev`) would still be live even if you had disabled your Worker’s `workers.dev` route. If you misinterpreted what it meant to disable your `workers.dev` route, you might unintentionally leave preview URLs enabled when you didn’t mean to, and expose them to the public Internet.
+
+To address this, we made a one-time update to disable preview URLs on existing Workers that had their workers.dev route disabled and changed the default behavior to be disabled for all new deployments where a preview URL setting was not explicitly configured.
+
+While this change helped secure many customers, it was also disruptive for customers who keep their `workers.dev` route enabled and actively use the preview functionality, as it now required them to explicitly enable preview URLs on every redeployment.
+T
+his new, more intuitive behavior ensures that your preview URL settings align with your `workers.dev` configuration by default, providing a more secure and predictable experience. 
+
+**Securing access to `workers.dev` and preview URL endpoints**
 
 To further secure your `workers.dev` subdomain and preview URL, you can [enable Cloudflare Access with a single click](/changelog/2025-10-03-one-click-access-for-workers/) in your Worker's settings to limit access to specific users or groups.