[Home](./index.md) > [@firebase/firestore](./firestore.md) > [/](./firestore_.md) > [setDoc](./firestore_.setdoc_1.md) ## setDoc() function Writes to the document referred to by the specified `DocumentReference`. If the document does not yet exist, it will be created. If you provide `merge` or `mergeFields`, the provided data can be merged into an existing document. Signature: ```typescript export declare function setDoc(reference: DocumentReference, data: Partial, options: SetOptions): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | reference | [DocumentReference](./firestore_.documentreference.md)<T> | A reference to the document to write. | | data | Partial<T> | A map of the fields and values for the document. | | options | [SetOptions](./firestore_.setoptions.md) | An object to configure the set behavior. | Returns: Promise<void> A Promise resolved once the data has been successfully written to the backend (note that it won't resolve while you're offline).