ListParts

ListParts shows the parts uploaded so far for a multipart upload started with CreateMultipartUpload, in part-number order, each with its size and ETag. Those ETags are exactly what CompleteMultipartUpload asks for, so ListParts is the natural way to see how far an upload has got and to gather what finishing it needs. A response holds up to 1,000 parts, and part-number-marker carries on to the next page.

Good to know on STRG

The permission is Write objects, the same one that uploads the parts, so a key that can upload can also check its progress. List objects on its own does not cover it.
Owner and Initiator both name your STRG account.
x-amz-expected-bucket-owner is welcome and has nothing to check: a key only ever reaches buckets of its own account.
A query parameter other than uploadId, max-parts and part-number-marker gets a clear answer straight away: STRG responds 501 NotImplemented.

When you'd use it

Resuming an interrupted upload. A desktop app sending a long video loses its connection halfway through. When it comes back, ListParts tells it which parts are already stored, so it sends only the rest and then completes the upload.
Collecting the ETags to finish an upload. A backup job that uploads parts from several workers at once does not need to pass every ETag back to one place: the process that completes the upload can read them all with ListParts.
Checking an upload left behind. A clean-up script that finds an unfinished upload with ListMultipartUploads can look at its parts - how many, how large, how recent - before deciding whether to finish it or abort it.

Request

GET /photos/2024/cat.jpg?uploadId=UploadId&max-parts=MaxParts&part-number-marker=PartNumberMarker HTTP/1.1
Host: my-bucket.s3.eu-central-1.strg.com
Authorization: AWS4-HMAC-SHA256 Credential=...
x-amz-date: 20260926T120000Z
x-amz-content-sha256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

The path-style form is GET /my-bucket/photos/2024/cat.jpg?uploadId=UploadId on s3.eu-central-1.strg.com - Addressing explains both.

Permissions

The access key needs Write objects (objects:write), the permission that uploads the parts, rather than List objects. For a key limited to certain buckets or to a key prefix, the bucket and the object key need to be within them. Access keys has the details.

URI parameters

Name	Type	Required	Description
`Bucket`	String	Yes	The bucket the upload was started in.
`Key`	String	Yes	The object key the upload was started for. A key with a `.` or `..` path segment (`a/../b`) cannot travel safely in a URL, and is answered `400 InvalidURI`.
`uploadId`	String	Yes	The upload ID that CreateMultipartUpload returned. Its presence is what makes this request ListParts rather than GetObject.
`max-parts`	Integer	No	The most parts to return. Up to 1,000, which is also the default.
`part-number-marker`	Integer	No	Lists only the parts with a higher part number. The previous response's `NextPartNumberMarker` goes here.

Any other query parameter is answered 501 NotImplemented.

Request headers

Name	Type	Required	Description
`x-amz-expected-bucket-owner`	String	No	Welcome, with nothing to check: an access key only ever reaches its own account's buckets.
`x-amz-request-payer`	String	No	Has no effect: STRG has no Requester Pays buckets.
`x-amz-server-side-encryption-customer-algorithm`	String	No	`AES256`, for an upload started with a customer-provided encryption key (SSE-C). Accepted.
`x-amz-server-side-encryption-customer-key`	String	No	The Base64 SSE-C key. Accepted.
`x-amz-server-side-encryption-customer-key-MD5`	String	No	Base64 MD5 of the SSE-C key. Accepted.

Request body

None.

Response

Response headers

Name	Description
`x-amz-request-id`	The request ID, useful when asking support about a request.

x-amz-request-charged is never returned. x-amz-abort-date and x-amz-abort-rule-id are not something to count on for whether a lifecycle rule will abort the upload; the bucket's rules, read with GetBucketLifecycleConfiguration, are the dependable answer.

Response body

Element	Description
`ListPartsResult`	The root element.
`Bucket`	The bucket name, as you use it.
`Key`	The object key.
`UploadId`	The upload ID.
`PartNumberMarker`	The `part-number-marker` of the request, `0` when none was sent.
`NextPartNumberMarker`	The last part number in this response - the `part-number-marker` for the next page.
`MaxParts`	The most parts this response could hold.
`IsTruncated`	`true` if more parts follow, in which case the next page starts after `NextPartNumberMarker`.
`Part`	One per part (`Parts` in the SDKs). Zero or more.
`Part` / `PartNumber`	The part number, 1-10,000.
`Part` / `LastModified`	When the part was uploaded.
`Part` / `ETag`	The part's entity tag, as UploadPart returned it - the value CompleteMultipartUpload takes for this part.
`Part` / `Size`	The part's size in bytes.
`Part` / `ChecksumCRC32`, `ChecksumCRC32C`, `ChecksumCRC64NVME`, `ChecksumSHA1`, `ChecksumSHA256`	The part's checksum, when one was stored for it.
`Initiator`	Who started the upload. `ID` and `DisplayName` both carry your STRG account ID.
`Owner`	The owner of the object to be created. `ID` and `DisplayName` both carry your STRG account ID.
`StorageClass`	Always `STANDARD`.
`ChecksumAlgorithm`	The checksum algorithm of the upload, when it has one.
`ChecksumType`	`COMPOSITE` or `FULL_OBJECT`, when the upload has a checksum.

<?xml version="1.0" encoding="UTF-8"?>
<ListPartsResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
  <Bucket>my-bucket</Bucket>
  <Key>photos/2024/cat.jpg</Key>
  <UploadId>example-upload-id</UploadId>
  <PartNumberMarker>0</PartNumberMarker>
  <NextPartNumberMarker>2</NextPartNumberMarker>
  <MaxParts>1000</MaxParts>
  <IsTruncated>false</IsTruncated>
  <Part>
    <ETag>"85f30635602dc09bd85957a6e82a2c21"</ETag>
    <LastModified>2026-09-26T12:00:05.000Z</LastModified>
    <PartNumber>1</PartNumber>
    <Size>67108864</Size>
  </Part>
  <Part>
    <ETag>"1b2cf535f27731c974343645a3985328"</ETag>
    <LastModified>2026-09-26T12:00:09.000Z</LastModified>
    <PartNumber>2</PartNumber>
    <Size>1048576</Size>
  </Part>
  <Initiator>
    <ID>your-account-id</ID>
    <DisplayName>your-account-id</DisplayName>
  </Initiator>
  <Owner>
    <ID>your-account-id</ID>
    <DisplayName>your-account-id</DisplayName>
  </Owner>
  <StorageClass>STANDARD</StorageClass>
</ListPartsResult>

Errors

These are the errors ListParts can return, and the situation behind each one.

Code	HTTP status	When
`NoSuchUpload`	404	The upload ID does not exist, or the upload was already completed or aborted.
`NoSuchBucket`	404	The bucket does not exist, it is in a region other than the endpoint's, or the account has no storage in this endpoint's region.
`AccessDenied`	403	The access key lacks Write objects, or the bucket or key is outside its buckets or prefix.
`InvalidAccessKeyId`	403	The access key does not exist, has expired or been revoked - or it was created moments ago and is not usable in this endpoint's region yet, in which case the same request works shortly afterwards.
`SignatureDoesNotMatch`	403	The request signature does not match.
`RequestTimeTooSkewed`	403	The request time is more than 15 minutes from the server's.
`AuthorizationHeaderMalformed`	400	The signature's credential scope names a region other than the endpoint's.
`InvalidURI`	400	The key contains a `.` or `..` path segment, such as `a/../b`.
`NotImplemented`	501	The request carries a query parameter this operation does not take.
`SlowDown`	503	Too many requests. The `Retry-After` header says when a retry is welcome; the AWS SDKs retry on their own.
`ServiceUnavailable`	503	A temporary failure; the same request can be retried.

Differences from Amazon S3

The table lists each place where STRG behaves differently, and what that means for a client.

Aspect	Amazon S3	STRG
Permission	`s3:ListMultipartUploadParts`	Write objects (`objects:write`), the permission that uploads the parts. List objects on its own does not cover it
`Owner`, `Initiator`	Your AWS canonical user ID, or an IAM user ARN	Your STRG account ID, in both `ID` and `DisplayName`
Bucket in another region	`301` redirect with `x-amz-bucket-region`	`404 NoSuchBucket`. A bucket is reached through its own regional endpoint.
`x-amz-expected-bucket-owner`	Checked against the bucket owner	Welcome, with nothing to check
Unknown query parameters	Ignored	`501 NotImplemented`, so a client knows straight away
Keys with `.` or `..` segments	Allowed	`400 InvalidURI`

Examples

Listing every part of an upload means following NextPartNumberMarker until IsTruncated is false - and the AWS CLI and the SDK paginators do that paging for you:

AWS CLI
Python (boto3)
JavaScript (AWS SDK v3)

aws s3api list-parts \
  --bucket my-bucket \
  --key photos/2024/cat.jpg \
  --upload-id "$UPLOAD_ID" \
  --endpoint-url https://s3.eu-central-1.strg.com \
  --region eu-central-1

import os

import boto3

s3 = boto3.client(
    "s3",
    endpoint_url="https://s3.eu-central-1.strg.com",
    region_name="eu-central-1",
)

paginator = s3.get_paginator("list_parts")
for page in paginator.paginate(
    Bucket="my-bucket",
    Key="photos/2024/cat.jpg",
    UploadId=os.environ["UPLOAD_ID"],
):
    for part in page.get("Parts", []):
        print(part["PartNumber"], part["Size"], part["ETag"])

import { S3Client, paginateListParts } from "@aws-sdk/client-s3";

const client = new S3Client({
  endpoint: "https://s3.eu-central-1.strg.com",
  region: "eu-central-1",
});

for await (const page of paginateListParts(
  { client },
  { Bucket: "my-bucket", Key: "photos/2024/cat.jpg", UploadId: process.env.UPLOAD_ID },
)) {
  for (const part of page.Parts ?? []) {
    console.log(part.PartNumber, part.Size, part.ETag);
  }
}

One page of at most 100 parts, starting after part 200:

AWS CLI
Python (boto3)
JavaScript (AWS SDK v3)

aws s3api list-parts \
  --bucket my-bucket \
  --key photos/2024/cat.jpg \
  --upload-id "$UPLOAD_ID" \
  --max-parts 100 \
  --part-number-marker 200 \
  --no-paginate \
  --endpoint-url https://s3.eu-central-1.strg.com \
  --region eu-central-1

import os

import boto3

s3 = boto3.client(
    "s3",
    endpoint_url="https://s3.eu-central-1.strg.com",
    region_name="eu-central-1",
)

response = s3.list_parts(
    Bucket="my-bucket",
    Key="photos/2024/cat.jpg",
    UploadId=os.environ["UPLOAD_ID"],
    MaxParts=100,
    PartNumberMarker=200,
)
for part in response.get("Parts", []):
    print(part["PartNumber"], part["ETag"])
if response["IsTruncated"]:
    print("next page starts after part", response["NextPartNumberMarker"])

import { ListPartsCommand, S3Client } from "@aws-sdk/client-s3";

const client = new S3Client({
  endpoint: "https://s3.eu-central-1.strg.com",
  region: "eu-central-1",
});

const response = await client.send(
  new ListPartsCommand({
    Bucket: "my-bucket",
    Key: "photos/2024/cat.jpg",
    UploadId: process.env.UPLOAD_ID,
    MaxParts: 100,
    PartNumberMarker: "200",
  }),
);
for (const part of response.Parts ?? []) {
  console.log(part.PartNumber, part.ETag);
}
if (response.IsTruncated) {
  console.log("next page starts after part", response.NextPartNumberMarker);
}

View as Markdown

When you'd use it​

Request​

Permissions​

URI parameters​

Request headers​

Request body​

Response​

Response headers​

Response body​

Errors​

Differences from Amazon S3​

Examples​

Related​