[Home](./index.md) > [@firebase/database](./database.md) > [useDatabaseEmulator](./database.usedatabaseemulator.md) ## useDatabaseEmulator() function Modify the provided instance to communicate with the Realtime Database emulator.

Note: This method must be called before performing any other operation. Signature: ```typescript export declare function useDatabaseEmulator(db: FirebaseDatabase, host: string, port: number): void; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | db | [FirebaseDatabase](./database.firebasedatabase.md) | The instance to modify. | | host | string | The emulator host (ex: localhost) | | port | number | The emulator port (ex: 8080) | Returns: void