---
title: aws-sdk-kotlin
description: Configure the AWS SDK for Kotlin to work with Cloudflare R2 object storage.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# aws-sdk-kotlin

You must [generate an Access Key](https://developers.cloudflare.com/r2/api/tokens/) before getting started. All examples will utilize `access_key_id` and `access_key_secret` variables which represent the **Access Key ID** and **Secret Access Key** values you generated.

  
This example uses the [aws-sdk-kotlin ↗](https://github.com/aws/aws-sdk-kotlin). You must pass in the R2 configuration credentials when instantiating your `S3` client:

## Basic Usage

Kotlin

```
import aws.sdk.kotlin.runtime.auth.credentials.StaticCredentialsProviderimport aws.sdk.kotlin.services.s3.S3Clientimport aws.sdk.kotlin.services.s3.listObjectsimport aws.sdk.kotlin.services.s3.model.GetObjectRequestimport aws.sdk.kotlin.services.s3.model.PutObjectRequestimport aws.sdk.kotlin.services.s3.presigners.presignGetObjectimport aws.sdk.kotlin.services.s3.presigners.presignPutObjectimport aws.smithy.kotlin.runtime.auth.awscredentials.Credentialsimport aws.smithy.kotlin.runtime.net.url.Urlimport kotlinx.coroutines.runBlockingimport kotlin.time.Duration.Companion.minutes
val ACCOUNT_ID = "<ACCOUNT_ID>"val ACCESS_KEY = "<ACCESS_KEY>"val SECRET_KEY = "<SECRET_KEY>"
fun main() = runBlocking {    val r2Client = S3Client.fromEnvironment {        region = "auto" // Required by SDK, but not used by R2        endpointUrl = Url.parse("https://${ACCOUNT_ID}.r2.cloudflarestorage.com")        credentialsProvider = StaticCredentialsProvider(            Credentials(                accessKeyId = ACCESS_KEY,                secretAccessKey = SECRET_KEY            ),        )    }
    println("Available buckets:")    r2Client.listBuckets().buckets?.forEach { bucket ->        println("* ${bucket.name}")    }
    val bucketName = "<BUCKET_NAME>"    println("\nObjects in bucket '${bucketName}':")    r2Client.listObjects { bucket = bucketName }.contents?.forEach {        println("* ${it.key} (size: ${it.size} bytes, modified: ${it.lastModified})")    }
    r2Client.close()}
```

```
Available buckets:* my-bucket-1* my-bucket-2
Objects in bucket 'my-bucket-1':* image1.png (size: 253167 bytes, modified: 2026-01-17T11:30:58.896Z)* image2.png (size: 247027 bytes, modified: 2026-01-17T11:30:57.779Z)
```

## Generate presigned URLs

You can also generate presigned links that can be used to temporarily share public read or write access to a bucket.

Kotlin

```
val uploadUrl = r2Client.presignPutObject(    input = PutObjectRequest {        bucket = bucketName        key = "README.md"    },    duration = 15.minutes,).urlprintln(uploadUrl)
val getUrl = r2Client.presignGetObject(    input = GetObjectRequest {        bucket = bucketName        key = "README.md"    },    duration = 15.minutes,).urlprintln(getUrl)
```

You can use these presigned URLs with any HTTP client. For example, to upload a file using the PUT URL:

Terminal window

```
curl -X PUT "https://<your-presigned-put-url>" -H "Content-Type: application/octet-stream" --data-binary "@local-file.txt"
```

To download a file using the GET URL:

Terminal window

```
curl -X GET "https://<your-presigned-get-url>" -o downloaded-file.txt
```

```json
{"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/r2/examples/aws/aws-sdk-kotlin/#page","headline":"aws-sdk-kotlin · Cloudflare R2 docs","description":"Configure the AWS SDK for Kotlin to work with Cloudflare R2 object storage.","url":"https://developers.cloudflare.com/r2/examples/aws/aws-sdk-kotlin/","inLanguage":"en","image":"https://developers.cloudflare.com/dev-products-preview.png","dateModified":"2026-04-21","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}}
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/r2/","name":"R2"}},{"@type":"ListItem","position":3,"item":{"@id":"/r2/examples/","name":"Examples"}},{"@type":"ListItem","position":4,"item":{"@id":"/r2/examples/aws/","name":"S3 SDKs"}},{"@type":"ListItem","position":5,"item":{"@id":"/r2/examples/aws/aws-sdk-kotlin/","name":"aws-sdk-kotlin"}}]}
```