---
title: "uploadPart | Grafana k6 documentation"
description: "S3Client.uploadPart a part in a multipart upload to a bucket"
---

# uploadPart

`S3Client.uploadPart` uploads a part to multipart upload in a bucket.

Expand table

| Parameter  | Type                  | Description                                 |
|------------|-----------------------|---------------------------------------------|
| bucketName | string                | Name of the bucket to upload the object to. |
| objectKey  | string                | Name of the object to upload.               |
| uploadId   | string                | UploadId of the multipart upload.           |
| partNumber | number                | The Part number of the Part to upload.      |
| data       | string \| ArrayBuffer | Content of the part to upload.              |

### Returns

Expand table

| Type                                                                                | Description                                                                                                                       |
|-------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------|
| Promise< [S3Part](/docs/k6/latest/javascript-api/jslib/aws/s3client/s3part/)> | A Promise that fulfills with a [S3Part](/docs/k6/latest/javascript-api/jslib/aws/s3client/s3part/) representing a S3 Part Upload. |

### Example

JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```javascript
import crypto from 'k6/crypto';
import exec from 'k6/execution';

import {
  AWSConfig,
  S3Client,
} from 'https://jslib.k6.io/aws/0.14.0/s3.js';

const awsConfig = new AWSConfig({
  region: __ENV.AWS_REGION,
  accessKeyId: __ENV.AWS_ACCESS_KEY_ID,
  secretAccessKey: __ENV.AWS_SECRET_ACCESS_KEY,
  sessionToken: __ENV.AWS_SESSION_TOKEN,
});

const s3 = new S3Client(awsConfig);

const testBucketName = 'test-jslib-aws';
const testFileKey = 'multipart.txt';

export default async function () {
  // Produce random bytes to upload of size ~12MB, that
  // we will upload in two 6MB parts. This is done as the
  // minimum part size supported by S3 is 5MB.
  const bigFile = crypto.randomBytes(12 * 1024 * 1024);

  // Initialize a multipart upload
  const multipartUpload = await s3.createMultipartUpload(testBucketName, testFileKey);

  // Upload the first part
  const firstPartData = bigFile.slice(0, 6 * 1024 * 1024);
  const firstPart = await s3.uploadPart(
    testBucketName,
    testFileKey,
    multipartUpload.uploadId,
    1,
    firstPartData
  );

  // Upload the second part
  const secondPartData = bigFile.slice(6 * 1024 * 1024, 12 * 1024 * 1024);
  const secondPart = await s3.uploadPart(
    testBucketName,
    testFileKey,
    multipartUpload.uploadId,
    2,
    secondPartData
  );

  // Complete the multipart upload
  await s3.completeMultipartUpload(testBucketName, testFileKey, multipartUpload.uploadId, [
    firstPart,
    secondPart,
  ]);

  // Let's redownload it verify it's correct, and delete it
  const obj = await s3.getObject(testBucketName, testFileKey);
  await s3.deleteObject(testBucketName, testFileKey);
}
```

*A k6 script that will upload a part in a multipart upload to an S3 bucket*