[Home](./index.md) > [@firebase/analytics](./analytics.md) > [setUserId](./analytics.setuserid.md) ## setUserId() function Use gtag 'config' command to set 'user\_id'. Signature: ```typescript export declare function setUserId(analyticsInstance: Analytics, id: string, options?: AnalyticsCallOptions): void; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | analyticsInstance | [Analytics](./analytics.analytics.md) | Firebase Analytics instance. | | id | string | User ID to set. | | options | [AnalyticsCallOptions](./analytics.analyticscalloptions.md) | | Returns: void