---
title: Match Workers subrequests by upstream zone — cf.worker.upstream_zone now supported in Transform Rules
description: Transform Rules now support the cf.worker.upstream_zone field, letting you conditionally apply rules based on which zone sent Workers subrequest.
image: https://developers.cloudflare.com/changelog-preview.png
---

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## Match Workers subrequests by upstream zone — cf.worker.upstream\_zone now supported in Transform Rules

Jun 09, 2025 

[ Rules ](https://developers.cloudflare.com/rules/) 

You can now use the [cf.worker.upstream\_zone](https://developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/cf.worker.upstream%5Fzone/) field in [Transform Rules](https://developers.cloudflare.com/rules/transform/) to control rule execution based on whether a request originates from [Workers](https://developers.cloudflare.com/workers/), including subrequests issued by Workers in other zones.

![Match Workers subrequests by upstream zone in Transform Rules](https://developers.cloudflare.com/_astro/transform-rule-subrequest-matching.BeUBEN67_wWefn.webp) 

**What's new:**

* `cf.worker.upstream_zone` is now supported in Transform Rules expressions.
* Skip or apply logic conditionally when handling [Workers subrequests](https://developers.cloudflare.com/workers/platform/limits/#subrequests).

For example, to add a header when the subrequest comes from another zone:

Text in **Expression Editor** (replace `myappexample.com` with your domain):

```
(cf.worker.upstream_zone != "" and cf.worker.upstream_zone != "myappexample.com")
```

Selected operation under **Modify request header**: _Set static_

**Header name**: `X-External-Workers-Subrequest`

**Value**: `1`

This gives you more granular control in how you handle incoming requests for your zone.

Learn more in the [Transform Rules](https://developers.cloudflare.com/rules/transform/) documentation and [Rules language fields](https://developers.cloudflare.com/ruleset-engine/rules-language/fields/reference/) reference.

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