---
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.StaticCredentialsProvider

import aws.sdk.kotlin.services.s3.S3Client

import aws.sdk.kotlin.services.s3.listObjects

import aws.sdk.kotlin.services.s3.model.GetObjectRequest

import aws.sdk.kotlin.services.s3.model.PutObjectRequest

import aws.sdk.kotlin.services.s3.presigners.presignGetObject

import aws.sdk.kotlin.services.s3.presigners.presignPutObject

import aws.smithy.kotlin.runtime.auth.awscredentials.Credentials

import aws.smithy.kotlin.runtime.net.url.Url

import kotlinx.coroutines.runBlocking

import 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,

).url

println(uploadUrl)


val getUrl = r2Client.presignGetObject(

    input = GetObjectRequest {

        bucket = bucketName

        key = "README.md"

    },

    duration = 15.minutes,

).url

println(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":"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"}}]}
```