[Home](./index.md) > [@firebase/firestore](./firestore.md) > [lite](./firestore_lite.md) > [collectionGroup](./firestore_lite.collectiongroup.md) ## collectionGroup() function Creates and returns a new `Query` instance that includes all documents in the database that are contained in a collection or subcollection with the given `collectionId`. Signature: ```typescript export declare function collectionGroup(firestore: FirebaseFirestore, collectionId: string): Query; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | firestore | [FirebaseFirestore](./firestore_lite.firebasefirestore.md) | A reference to the root Firestore instance. | | collectionId | string | Identifies the collections to query over. Every collection or subcollection with this ID as the last segment of its path will be included. Cannot contain a slash. | Returns: [Query](./firestore_lite.query.md)<[DocumentData](./firestore_lite.documentdata.md)> The created `Query`.