[Home](./index.md) > [@firebase/storage](./storage.md) > [UploadTask](./storage.uploadtask.md) > [then](./storage.uploadtask.then.md) ## UploadTask.then() method This object behaves like a Promise, and resolves with its snapshot data when the upload completes. Signature: ```typescript then(onFulfilled?: ((snapshot: UploadTaskSnapshot) => unknown) | null, onRejected?: ((error: FirebaseStorageError) => unknown) | null): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | onFulfilled | ((snapshot: [UploadTaskSnapshot](./storage.uploadtasksnapshot.md)) => unknown) \| null | The fulfillment callback. Promise chaining works as normal. | | onRejected | ((error: [FirebaseStorageError](./storage.firebasestorageerror.md)) => unknown) \| null | The rejection callback. | Returns: Promise<unknown>