[Home](./index.md) > [@snowplow/browser-tracker](./browser-tracker.md) > [BrowserTracker](./browser-tracker.browsertracker.md) > [setUserIdFromReferrer](./browser-tracker.browsertracker.setuseridfromreferrer.md) ## BrowserTracker.setUserIdFromReferrer property Set the business-defined user ID for this user using the referrer querystring. Signature: ```typescript setUserIdFromReferrer: (querystringField: string) => void; ```