---
sidebar_position: 4
slug: /aws-s3-multipart
---

import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
import UppyCdnExample from '/src/components/UppyCdnExample';

# AWS S3

The `@uppy/aws-s3` plugin can be used to upload files directly to a S3 bucket or
a S3-compatible provider, such as Google Cloud Storage or DigitalOcean Spaces.
Uploads can be signed using either [Companion][companion docs], temporary
credentials, or a custom signing function.

## When should I use it?

:::tip

Not sure which uploader is best for you? Read
“[Choosing the uploader you need](/docs/guides/choosing-uploader)”.

:::

You can use this plugin when you prefer a _client-to-storage_ over a
_client-to-server-to-storage_ (such as [Transloadit](/docs/transloadit) or
[Tus](/docs/tus)) setup. This may in some cases be preferable, for instance, to
reduce costs or the complexity of running a server and load balancer with
[Tus](/docs/tus).

Multipart uploads start to become valuable for larger files (100&nbsp;MiB+) as
it uploads a single object as a set of parts. This has certain benefits, such as
improved throughput (uploading parts in parallel) and quick recovery from
network issues (only the failed parts need to be retried). The downside is
request overhead, as it needs to do creation, signing (unless you are [signing
on the client][]), and completion requests besides the upload requests. For
example, if you are uploading files that are only a couple kilobytes with a
100ms roundtrip latency, you are spending 400ms on overhead and only a few
milliseconds on uploading.

**In short**

- We recommend the default value of [`shouldUseMultipart`][], which enable
  multipart uploads only for large files.
- If you prefer to have less overhead (+20% upload speed) you can use temporary
  S3 credentials with [`getTemporarySecurityCredentials`][]. This means users
  get a single token which allows them to do bucket operations for longer,
  instead of short lived signed URL per resource. This is a security trade-off.

## Install

<Tabs>
  <TabItem value="npm" label="NPM" default>

```shell
npm install @uppy/aws-s3
```

  </TabItem>

  <TabItem value="yarn" label="Yarn">

```shell
yarn add @uppy/aws-s3
```

  </TabItem>

  <TabItem value="cdn" label="CDN">
    <UppyCdnExample>
      {`
        import { Uppy, AwsS3 } from "{{UPPY_JS_URL}}"
        new Uppy().use(AwsS3, { /* see options */ })
      `}
    </UppyCdnExample>
  </TabItem>
</Tabs>

## Use

### Setting up your S3 bucket

To use this plugin with S3 we need to setup a bucket with the right permissions
and CORS settings.

S3 buckets do not allow public uploads for security reasons. To allow Uppy and
the browser to upload directly to a bucket, its CORS permissions need to be
configured.

CORS permissions can be found in the
[S3 Management Console](https://console.aws.amazon.com/s3/home). Click the
bucket that will receive the uploads, then go into the `Permissions` tab and
select the `CORS configuration` button. A JSON document will be shown that
defines the CORS configuration. (AWS used to use XML but now only allow JSON).
More information about the
[S3 CORS format here](https://docs.amazonaws.cn/en_us/AmazonS3/latest/userguide/ManageCorsUsing.html).

The configuration required for Uppy and Companion is this:

```json
[
	{
		"AllowedOrigins": ["https://my-app.com"],
		"AllowedMethods": ["GET", "PUT"],
		"MaxAgeSeconds": 3000,
		"AllowedHeaders": [
			"Authorization",
			"x-amz-date",
			"x-amz-content-sha256",
			"content-type"
		],
		"ExposeHeaders": ["ETag", "Location"]
	},
	{
		"AllowedOrigins": ["*"],
		"AllowedMethods": ["GET"],
		"MaxAgeSeconds": 3000
	}
]
```

A good practice is to use two CORS rules: one for viewing the uploaded files,
and one for uploading files. This is done above where the first object in the
array defines the rules for uploading, and the second for viewing. The example
above **makes files publicly viewable**. You can change it according to your
needs.

If you are using an IAM policy to allow access to the S3 bucket, the policy must
have at least the `s3:PutObject` and `s3:PutObjectAcl` permissions scoped to the
bucket in question. In-depth documentation about CORS rules is available on the
[AWS documentation site](https://docs.aws.amazon.com/AmazonS3/latest/dev/cors.html).

### Use with your own server

The recommended approach is to integrate `@uppy/aws-s3` with your own server.
You will need to do the following things:

1. [Setup a S3 bucket](#setting-up-your-s3-bucket).
2. [Setup your server](https://github.com/transloadit/uppy/blob/main/examples/aws-nodejs/index.js)
3. [Setup Uppy client](https://github.com/transloadit/uppy/blob/main/examples/aws-nodejs/public/index.html).

### Use with Companion

[Companion](/docs/companion) has S3 routes built-in for a plug-and-play
experience with Uppy.

:::caution

Generally it’s better for access control, observability, and scaling to
integrate `@uppy/aws-s3` with your own server. You may want to use
[Companion](/docs/companion) for creating, signing, and completing your S3
uploads if you already need Companion for remote files (such as from Google
Drive). Otherwise it’s not worth the hosting effort.

:::

```js {10} showLineNumbers
import Uppy from '@uppy/core';
import Dashboard from '@uppy/dashboard';
import AwsS3 from '@uppy/aws-s3';

import '@uppy/core/dist/style.min.css';
import '@uppy/dashboard/dist/style.min.css';

const uppy = new Uppy()
	.use(Dashboard, { inline: true, target: 'body' })
	.use(AwsS3, {
		companionUrl: 'https://companion.uppy.io',
	});
```

## API

### Options

#### `shouldUseMultipart(file)`

A boolean, or a function that returns a boolean which is called for each file
that is uploaded with the corresponding `UppyFile` instance as argument.

By default, all files with a `file.size` ≤ 100&nbsp;MiB will be uploaded in a
single chunk, all files larger than that as multipart.

Here’s how to use it:

```js
uppy.use(AwsS3, {
	shouldUseMultipart(file) {
		// Use multipart only for files larger than 100MiB.
		return file.size > 100 * 2 ** 20;
	},
});
```

#### `limit`

The maximum amount of files to upload in parallel (`number`, default: `6`).

Note that the amount of files is not the same as the amount of concurrent
connections. Multipart uploads can use many requests per file. For example, for
a 100 MiB file with a part size of 5 MiB:

- 1 `createMultipartUpload` request
- 100/5 = 20 sign requests (unless you are [signing on the client][])
- 100/5 = 20 upload requests
- 1 `completeMultipartUpload` request

:::caution

Unless you have a good reason and are well informed about the average internet
speed of your users, do not set this higher. S3 uses HTTP/1.1, which means a
limit to concurrent connections and your uploads may expire before they are
uploaded.

:::

#### `companionUrl`

URL to a [Companion](/docs/companion) instance (`string`, default: `null`).

#### `companionHeaders`

Custom headers that should be sent along to [Companion](/docs/companion) on
every request (`Object`, default: `{}`).

#### `companionCookiesRule`

This option correlates to the
[RequestCredentials value](https://developer.mozilla.org/en-US/docs/Web/API/Request/credentials)
(`string`, default: `'same-origin'`).

This tells the plugin whether to send cookies to [Companion](/docs/companion).

#### `retryDelays`

`retryDelays` are the intervals in milliseconds used to retry a failed chunk
(`array`, default: `[0, 1000, 3000, 5000]`).

This is also used for [`signPart()`](#signpartfile-partdata). Set to `null` to
disable automatic retries, and fail instantly if any chunk fails to upload.

#### `getChunkSize(file)`

A function that returns the minimum chunk size to use when uploading the given
file as multipart.

For multipart uploads, chunks are sent in batches to have presigned URLs
generated with [`signPart()`](#signpartfile-partdata). To reduce the amount of
requests for large files, you can choose a larger chunk size, at the cost of
having to re-upload more data if one chunk fails to upload.

S3 requires a minimum chunk size of 5MiB, and supports at most 10,000 chunks per
multipart upload. If `getChunkSize()` returns a size that’s too small, Uppy will
increase it to S3’s minimum requirements.

#### `getUploadParameters(file, options)`

:::note

When using [Companion][companion docs] to sign S3 uploads, you should not define
this option.

:::

A function that will be called for each non-multipart upload.

- `file`: `UppyFile` the file that will be uploaded
- `options`: `object`
  - `signal`: `AbortSignal`
- **Returns:** `object | Promise<object>`
  - `method`: `string`, the HTTP method to be used for the upload. This should
    be one of either `PUT` or `POST`, depending on the type of upload used.
  - `url`: `string`, the URL to which the upload request will be sent. When
    using a presigned PUT upload, this should be the URL to the S3 object with
    signing parameters included in the query string. When using a POST upload
    with a policy document, this should be the root URL of the bucket.
  - `fields` `object`, an object with form fields to send along with the upload
    request. For presigned PUT uploads (which are default), this should be left
    empty.
  - `headers`: `object`, an object with request headers to send along with the
    upload request. When using a presigned PUT upload, it’s a good idea to
    provide `headers['content-type']`. That will make sure that the request uses
    the same content-type that was used to generate the signature. Without it,
    the browser may decide on a different content-type instead, causing S3 to
    reject the upload.

#### `createMultipartUpload(file)`

A function that calls the S3 Multipart API to create a new upload.

`file` is the file object from Uppy’s state. The most relevant keys are
`file.name` and `file.type`.

Return a Promise for an object with keys:

- `uploadId` - The UploadID returned by S3.
- `key` - The object key for the file. This needs to be returned to allow it to
  be different from the `file.name`.

The default implementation calls out to Companion’s S3 signing endpoints.

#### `listParts(file, { uploadId, key })`

A function that calls the S3 Multipart API to list the parts of a file that have
already been uploaded.

Receives the `file` object from Uppy’s state, and an object with keys:

- `uploadId` - The UploadID of this Multipart upload.
- `key` - The object key of this Multipart upload.

Return a Promise for an array of S3 Part objects, as returned by the S3
Multipart API. Each object has keys:

- `PartNumber` - The index in the file of the uploaded part.
- `Size` - The size of the part in bytes.
- `ETag` - The ETag of the part, used to identify it when completing the
  multipart upload and combining all parts into a single file.

The default implementation calls out to Companion’s S3 signing endpoints.

#### `signPart(file, partData)`

A function that generates a signed URL for the specified part number. The
`partData` argument is an object with the keys:

- `uploadId` - The UploadID of this Multipart upload.
- `key` - The object key in the S3 bucket.
- `partNumber` - can’t be zero.
- `body` – The data that will be signed.
- `signal` – An `AbortSignal` that may be used to abort an ongoing request.

This function should return a object, or a promise that resolves to an object,
with the following keys:

- `url` – the presigned URL, as a `string`.
- `headers` – **(Optional)** Custom headers to send along with the request to S3
  endpoint.

An example of what the return value should look like:

```json
{
	"url": "https://bucket.region.amazonaws.com/path/to/file.jpg?partNumber=1&...",
	"headers": { "Content-MD5": "foo" }
}
```

#### `abortMultipartUpload(file, { uploadId, key })`

A function that calls the S3 Multipart API to abort a Multipart upload, and
removes all parts that have been uploaded so far.

Receives the `file` object from Uppy’s state, and an object with keys:

- `uploadId` - The UploadID of this Multipart upload.
- `key` - The object key of this Multipart upload.

This is typically called when the user cancels an upload. Cancellation cannot
fail in Uppy, so the result of this function is ignored.

The default implementation calls out to Companion’s S3 signing endpoints.

#### `completeMultipartUpload(file, { uploadId, key, parts })`

A function that calls the S3 Multipart API to complete a Multipart upload,
combining all parts into a single object in the S3 bucket.

Receives the `file` object from Uppy’s state, and an object with keys:

- `uploadId` - The UploadID of this Multipart upload.
- `key` - The object key of this Multipart upload.
- `parts` - S3-style list of parts, an array of objects with `ETag` and
  `PartNumber` properties. This can be passed straight to S3’s Multipart API.

Return a Promise for an object with properties:

- `location` - **(Optional)** A publicly accessible URL to the object in the S3
  bucket.

The default implementation calls out to Companion’s S3 signing endpoints.

#### `allowedMetaFields: null`

Pass an array of field names to limit the metadata fields that will be added to
upload as query parameters.

- Set it to `false` to not send any fields (or an empty array).
- Set it to `['name']` to only send the `name` field.
- Set it to `true` (the default) to send _all_ metadata fields.

<details>
<summary>Deprecated options</summary>

#### `getTemporarySecurityCredentials(options)`

:::note

When using [Companion][companion docs] as a backend, you can pass `true` instead
of a function. Setting up Companion will not simplify the process of getting
signing on the client.

:::

A boolean (when using Companion), or an (async) function to retrieve temporary
security credentials used for all uploads instead of signing every part. This
results in less request overhead which can lead to around 20% faster uploads.
This is a security tradeoff. We recommend to not use this option unless you are
familiar with the security implications of temporary credentials, and how to
setup your bucket to make it work. See the
[Requesting temporary security credentials](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_request.html)
AWS guide for more information.

It’s strongly recommended to have some sort of caching process to avoid
requesting more temporary token than necessary.

- `options`: `object`
  - `signal`: `AbortSignal`
- **Returns:** `object | Promise<object>`
  - `credentials`: `object`
    - `AccessKeyId`: `string`
    - `SecretAccessKey`: `string`
    - `SessionToken`: `string`
    - `Expiration`: `string`
  - `bucket`: `string`
  - `region`: `string`

If you are using Companion (for example because you want to support remote
upload sources), you can pass a boolean:

```js
uppy.use(AwsS3, {
	// This is an example using Companion:
	companionUrl: 'http://companion.uppy.io',
	getTemporarySecurityCredentials: true,
	shouldUseMultipart: (file) => file.size > 100 * 2 ** 20,
});
```

In the most common case, you are using a different backend, in which case you
need to specify a function:

```js
uppy.use(AwsS3, {
	// This is an example not using Companion:
	async getTemporarySecurityCredentials({ signal }) {
		const response = await fetch('/sts-token', { signal });
		if (!response.ok)
			throw new Error('Failed to fetch STS', { cause: response });
		return response.json();
	},
	shouldUseMultipart: (file) => file.size > 100 * 2 ** 20,
});
```

</details>

[`gettemporarysecuritycredentials`]: #gettemporarysecuritycredentialsoptions
[`shouldusemultipart`]: #shouldusemultipartfile
[companion docs]: /docs/companion
[signing on the client]: #gettemporarysecuritycredentialsoptions
