---
title: "FileUpload"
source: "https://github.com/remix-run/remix/blob/8905f3943706e1f53696ab83e70a84873cabfc90/packages/form-data-parser/src/lib/future/form-data.ts#L39"
---

# FileUpload

## Summary

A file that was uploaded as part of a `multipart/form-data` request, passed to a
[`FileUploadHandler`](/form-data-parser/future/interface/FileUploadHandler/) as soon as its headers arrive.

Its contents are streamed from the request as you read them, so you can store large uploads
without holding them in memory. It has the properties and methods of a
[`File`](https://developer.mozilla.org/en-US/docs/Web/API/File), with these differences:

- Its contents can only be read once, with `stream()`, `bytes()`, `arrayBuffer()`, or `text()`
- `size` throws until its contents have been read; limit upload size with `maxFileSize`
- `slice()` is not supported
- It is not a `File` instance, so pass `stream()` to APIs that read a `File` natively, like
  `new Response()`

The `name` and `type` properties are untrusted client input from the submitted multipart metadata;
they do not validate the file contents. The `name` is not sanitized for filesystem use and must
not be used directly as a filesystem path, including on files returned in `FormData`. Generate
storage names and validate file contents in your upload handler before using files in
application-specific contexts.

## Signature

```ts
class FileUpload {
  constructor(part: MultipartPart, fieldName: string): FileUpload

  // Properties
  fieldName: string
  lastModified: number
  name: string
  type: string
  webkitRelativePath: ''

  // Accessors
  get [toStringTag](): string
  get size(): number

  // Methods
  arrayBuffer(): Promise<ArrayBuffer>
  bytes(): Promise<Uint8Array<ArrayBuffer>>
  formData(): Promise<FormData>
  json(): Promise<any>
  slice(): never
  stream(): ReadableStream<Uint8Array<ArrayBuffer>>
  text(): Promise<string>
  toString(): never
}

```

## Constructor

### Parameters

#### `part`

The multipart part containing the file

#### `fieldName`

The name of the `<input>` field used to upload the file

## Properties

### `fieldName`

The name of the `<input>` field used to upload the file.

### `lastModified`

The time the upload was received, in milliseconds since the Unix epoch.

### `name`

The name of the file, from the multipart `Content-Disposition` header.

### `type`

The media type of the file, from the multipart `Content-Type` header.

### `webkitRelativePath`

Always an empty string.

## Accessors

### `[toStringTag]`

### `size`

The size of the file in bytes. Throws until the file's contents have been read.

## Methods

### `arrayBuffer(): Promise<ArrayBuffer>`

Reads the file's contents into an `ArrayBuffer`.



### `bytes(): Promise<Uint8Array<ArrayBuffer>>`

Reads the file's contents into a `Uint8Array`.



### `formData(): Promise<FormData>`

Parses the file's contents as form data, using its `type` as the content type.



### `json(): Promise<any>`

Parses the file's contents as JSON.



### `slice(): never`

Not supported, because the file's contents are streamed from the request.



### `stream(): ReadableStream<Uint8Array<ArrayBuffer>>`

Returns a stream of the file's contents.



### `text(): Promise<string>`

Reads the file's contents as a UTF-8 string.



### `toString(): never`

Throws, so a file upload isn't silently converted to a string by APIs that expect a `File`,
like `FormData#append()` or `new Response()`.