---
title: cf.worker.upstream_zone
description: Identifies whether a request comes from a worker or not.
image: https://developers.cloudflare.com/core-services-preview.png
---

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#  cf.worker.upstream\_zone 

`cf.worker.upstream_zone` ` String ` 

Identifies whether a request comes from a worker or not.

When a request comes from a worker, this field will hold the name of the zone for that worker. Otherwise, `cf.worker.upstream_zone` is empty.

Categories: 
* Request

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