---
title: "Initiate a Multipart Upload"
slug: "initiate-a-multipart-upload-s3cmd-tg"
tags: ["5.4"]
updated: 2026-10-28T01:54:14Z
published: 2026-10-28T01:54:14Z
canonical: "docs.vastdata.com/initiate-a-multipart-upload-s3cmd-tg"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Initiate a Multipart Upload

Multipart uploads are automatically used when a file to upload is larger than 15MB. The file is split into multiple parts, with each part of 15MB in size (the last part can be smaller). Each part is uploaded separately. The file is reconstructed at the destination when the transfer is completed. If an upload of a part fails, it can be restarted without affecting any of the other parts already uploaded.

```plaintext
s3cmd [-c CONFIGFILE] put [--multipart-chunk-size-mb=SIZE] FILE  s3://BUCKET[/PREFIX]
```

| CONFIGFILE | Configuration file. Defaults to $HOME/.s3cfg |
| --- | --- |
| SIZE | Size of each chunk of a multipart upload. Files bigger than SIZE are automatically uploaded as multithreaded-multipart, smaller files are uploaded using the traditional method. SIZE is in Mega-Bytes, default chunk size is 15MB, minimum allowed chunk size is 5MB, maximum is 5GB. |
| FILE | A file over 15 MB in size. (If smaller, the file will be uploaded without being split into parts.) |
| BUCKET | The bucket to which to upload the file. |
| PREFIX | Prefix to append to the object name from which file system hierarchy can be inferred. When listing objects in the bucket, the prefix can be used to filter the list. You can specify a nested series of prefixes delimited by the delimiter (which is typically '/'). Object listing can be filtered by prefixes and delimiters. See [List Objects in a Bucket](/docs-5-4/docs/en/list-objects-in-a-bucket-s3cmd-tg). For example, when uploading a file called *file.asp*, if you specify a prefix */dev/misc* the complete S3 object key becomes *dev/misc/file.asp*. A file system hierarchy can be inferred consisting of a folder called *misc* nested under a folder called *dev* in which the file *file.asp* is contained. |

## Example

Start uploading the large file *Big.zip* in parts of 500 MB:

```plaintext
$ s3cmd -c  vast.s3cfg put --multipart-chunk-size-mb=500 Big.zip s3://mybucket/
upload: 'Big.zip' > 's3://mybucket/Big.zip' [part 1 of 16, 500MB] [1 of 1]
```