Use PutBucketWebsite with an Amazon SDK or CLI

                // Put the website configuration.
                PutBucketWebsiteRequest putRequest = new PutBucketWebsiteRequest()
                {
                    BucketName = bucketName,
                    WebsiteConfiguration = new WebsiteConfiguration()
                    {
                        IndexDocumentSuffix = indexDocumentSuffix,
                        ErrorDocument = errorDocument,
                    },
                };
                PutBucketWebsiteResponse response = await client.PutBucketWebsiteAsync(putRequest);

bool AwsDoc::S3::PutWebsiteConfig(const Aws::String &bucketName,
                                  const Aws::String &indexPage, const Aws::String &errorPage,
                                  const Aws::Client::ClientConfiguration &clientConfig) {
    Aws::S3::S3Client client(clientConfig);

    Aws::S3::Model::IndexDocument indexDocument;
    indexDocument.SetSuffix(indexPage);

    Aws::S3::Model::ErrorDocument errorDocument;
    errorDocument.SetKey(errorPage);

    Aws::S3::Model::WebsiteConfiguration websiteConfiguration;
    websiteConfiguration.SetIndexDocument(indexDocument);
    websiteConfiguration.SetErrorDocument(errorDocument);

    Aws::S3::Model::PutBucketWebsiteRequest request;
    request.SetBucket(bucketName);
    request.SetWebsiteConfiguration(websiteConfiguration);

    Aws::S3::Model::PutBucketWebsiteOutcome outcome =
            client.PutBucketWebsite(request);

    if (!outcome.IsSuccess()) {
        std::cerr << "Error: PutBucketWebsite: "
                  << outcome.GetError().GetMessage() << std::endl;
    }
    else {
        std::cout << "Success: Set website configuration for bucket '"
                  << bucketName << "'." << std::endl;
    }

    return outcome.IsSuccess();
}

The applies a static website configuration to a bucket named my-bucket:

aws s3api put-bucket-website --bucket my-bucket --website-configuration file://website.json

The file website.json is a JSON document in the current folder that specifies index and error pages for the website:

{
    "IndexDocument": {
        "Suffix": "index.html"
    },
    "ErrorDocument": {
        "Key": "error.html"
    }
}

import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.IndexDocument;
import software.amazon.awssdk.services.s3.model.PutBucketWebsiteRequest;
import software.amazon.awssdk.services.s3.model.WebsiteConfiguration;
import software.amazon.awssdk.services.s3.model.S3Exception;
import software.amazon.awssdk.regions.Region;

/**
 * Before running this Java V2 code example, set up your development
 * environment, including your credentials.
 *
 * For more information, see the following documentation topic:
 *
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */

public class SetWebsiteConfiguration {
    public static void main(String[] args) {
        final String usage = """

                Usage:    <bucketName> [indexdoc]\s

                Where:
                   bucketName   - The Amazon S3 bucket to set the website configuration on.\s
                   indexdoc - The index document, ex. 'index.html'
                              If not specified, 'index.html' will be set.
                """;

        if (args.length != 1) {
            System.out.println(usage);
            System.exit(1);
        }

        String bucketName = args[0];
        String indexDoc = "index.html";
        Region region = Region.US_EAST_1;
        S3Client s3 = S3Client.builder()
                .region(region)
                .build();

        setWebsiteConfig(s3, bucketName, indexDoc);
        s3.close();
    }

    public static void setWebsiteConfig(S3Client s3, String bucketName, String indexDoc) {
        try {
            WebsiteConfiguration websiteConfig = WebsiteConfiguration.builder()
                    .indexDocument(IndexDocument.builder().suffix(indexDoc).build())
                    .build();

            PutBucketWebsiteRequest pubWebsiteReq = PutBucketWebsiteRequest.builder()
                    .bucket(bucketName)
                    .websiteConfiguration(websiteConfig)
                    .build();

            s3.putBucketWebsite(pubWebsiteReq);
            System.out.println("The call was successful");

        } catch (S3Exception e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
    }
}

Set the website configuration.

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

const client = new S3Client({});

// Set up a bucket as a static website.
// The bucket needs to be publicly accessible.
export const main = async () => {
  const command = new PutBucketWebsiteCommand({
    Bucket: "test-bucket",
    WebsiteConfiguration: {
      ErrorDocument: {
        // The object key name to use when a 4XX class error occurs.
        Key: "error.html",
      },
      IndexDocument: {
        // A suffix that is appended to a request that is for a directory.
        Suffix: "index.html",
      },
    },
  });

  try {
    const response = await client.send(command);
    console.log(response);
  } catch (err) {
    console.error(err);
  }
};

Example 1: The command enables website hosting for the given bucket with the index document as 'index.html' and error document as 'error.html'.

Write-S3BucketWebsite -BucketName 's3testbucket' -WebsiteConfiguration_IndexDocumentSuffix 'index.html' -WebsiteConfiguration_ErrorDocument 'error.html'

require "aws-sdk-s3"

# Wraps Amazon S3 bucket website actions.
class BucketWebsiteWrapper
  attr_reader :bucket_website

  # @param bucket_website [Aws::S3::BucketWebsite] A bucket website object configured with an existing bucket.
  def initialize(bucket_website)
    @bucket_website = bucket_website
  end

  # Sets a bucket as a static website.
  #
  # @param index_document [String] The name of the index document for the website.
  # @param error_document [String] The name of the error document to show for 4XX errors.
  # @return [Boolean] True when the bucket is configured as a website; otherwise, false.
  def set_website(index_document, error_document)
    @bucket_website.put(
      website_configuration: {
        index_document: { suffix: index_document },
        error_document: { key: error_document }
      }
    )
    true
  rescue Aws::Errors::ServiceError => e
    puts "Couldn't configure #{@bucket_website.bucket.name} as a website. Here's why: #{e.message}"
    false
  end
end

# Example usage:
def run_demo
  bucket_name = "doc-example-bucket"
  index_document = "index.html"
  error_document = "404.html"

  wrapper = BucketWebsiteWrapper.new(Aws::S3::BucketWebsite.new(bucket_name))
  return unless wrapper.set_website(index_document, error_document)

  puts "Successfully configured bucket #{bucket_name} as a static website."
end

run_demo if $PROGRAM_NAME == __FILE__