aws-sdk-net

Last updated Apr 21, 2026 You must generate an Access Key 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 version 3 of the aws-sdk-net ↗︎ package. You must pass in the R2 configuration credentials when instantiating your S3 service client:

Client setup

In this example, you will pass credentials explicitly to the IAmazonS3 initialization. If you wish, use a shared AWS credentials file or the SDK store in-line with other AWS SDKs. Refer to Configure AWS credentials ↗︎ for more details.

private static IAmazonS3 s3Client;

public static void Main(string[] args)
{
    // Retrieve your S3 API credentials for your R2 bucket via API tokens (see: https://developers.cloudflare.com/r2/api/tokens)
    var accessKey = "<ACCESS_KEY_ID>";
    var secretKey = "<SECRET_ACCESS_KEY>";
    var credentials = new BasicAWSCredentials(accessKey, secretKey);
    s3Client = new AmazonS3Client(credentials, new AmazonS3Config
        {
            // Provide your Cloudflare account ID
            ServiceURL = "https://<ACCOUNT_ID>.r2.cloudflarestorage.com",
        });
}

List buckets and objects

The ListBucketsAsync ↗︎ and ListObjectsAsync ↗︎ methods can be used to list buckets under your account and the contents of those buckets respectively.

static async Task ListBuckets()
{
    var response = await s3Client.ListBucketsAsync();

    foreach (var s3Bucket in response.Buckets)
    {
        Console.WriteLine("{0}", s3Bucket.BucketName);
    }
}

sdk-example
my-bucket

static async Task ListObjectsV2()
{
    var request = new ListObjectsV2Request
    {
        BucketName = "my-bucket"
    };

    var response = await s3Client.ListObjectsV2Async(request);

    foreach (var s3Object in response.S3Objects)
    {
        Console.WriteLine("{0}", s3Object.Key);
    }
}

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Upload and retrieve objects

The PutObjectAsync ↗︎ and GetObjectAsync ↗︎ methods can be used to upload objects and download objects from an R2 bucket respectively.

Caution

DisablePayloadSigning = true and DisableDefaultChecksumValidation = true must be passed as Cloudflare R2 does not currently support the Streaming SigV4 implementation used by AWSSDK.S3.

static async Task PutObject()
{
    var request = new PutObjectRequest
    {
        FilePath = @"/path/file.txt",
        BucketName = "my-bucket",
        DisablePayloadSigning = true,
        DisableDefaultChecksumValidation = true
    };

    var response = await s3Client.PutObjectAsync(request);

    Console.WriteLine("ETag: {0}", response.ETag);
}

ETag: "186a71ee365d9686c3b98b6976e1f196"

static async Task GetObject()
{
    var bucket = "my-bucket";
    var key = "file.txt";

    var response = await s3Client.GetObjectAsync(bucket, key);

    Console.WriteLine("ETag: {0}", response.ETag);
}

ETag: "186a71ee365d9686c3b98b6976e1f196"

Generate presigned URLs

The GetPreSignedURL ↗︎ method allows you to sign ahead of time, giving temporary access to a specific operation. In this case, presigning a PutObject request for sdk-example/file.txt.

static string? GeneratePresignedUrl()
{
    AWSConfigsS3.UseSignatureVersion4 = true;
    var presign = new GetPreSignedUrlRequest
    {
        BucketName = "my-bucket",
        Key = "file.txt",
        Verb = HttpVerb.GET,
        Expires = DateTime.Now.AddDays(7),
    };

    var presignedUrl = s3Client.GetPreSignedURL(presign);

    Console.WriteLine(presignedUrl);

    return presignedUrl;
}

https://<ACCOUNT_ID>.r2.cloudflarestorage.com/my-bucket/file.txt?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=<credential>&X-Amz-Date=<timestamp>&X-Amz-Expires=3600&X-Amz-SignedHeaders=host&X-Amz-Signature=<signature>

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