[Home](./index.md) > [@firebase/functions](./functions.md) > [useFunctionsEmulator](./functions.usefunctionsemulator.md) ## useFunctionsEmulator() function Modify this instance to communicate with the Cloud Functions emulator. Note: this must be called before this instance has been used to do any operations. Signature: ```typescript export declare function useFunctionsEmulator(functionsInstance: Functions, host: string, port: number): void; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | functionsInstance | [Functions](./functions.functions.md) | | | host | string | The emulator host (ex: localhost) | | port | number | The emulator port (ex: 5001) | Returns: void