Virtual hosting of buckets - Amazon Simple Storage Service

Virtual hosting of buckets

Virtual hosting is the practice of serving multiple websites from a single web server. One way to differentiate sites in your Amazon S3 REST API requests is by using the apparent hostname of the Request-URI instead of just the path name part of the URI. An ordinary Amazon S3 REST request specifies a bucket by using the first slash-delimited component of the Request-URI path. Instead, you can use Amazon S3 virtual hosting to address a bucket in a REST API call by using the HTTP Host header. In practice, Amazon S3 interprets Host as meaning that most buckets are automatically accessible for limited types of requests at https://bucket-name.s3.region-code.amazonaws.com. For a complete list of Amazon S3 Regions and endpoints, see Amazon S3 endpoints and quotas in the Amazon Web Services General Reference.

Virtual hosting also has other benefits. By naming your bucket after your registered domain name and by making that name a DNS alias for Amazon S3, you can completely customize the URL of your Amazon S3 resources, for example, http://my.bucket-name.com/. You can also publish to the "root directory" of your bucket's virtual server. This ability can be important because many existing applications search for files in this standard location. For example, favicon.ico, robots.txt, and crossdomain.xml are all expected to be found at the root.

Important

When you're using virtual-hosted–style buckets with SSL, the SSL wildcard certificate matches only buckets that do not contain dots (.). To work around this limitation, use HTTP or write your own certificate-verification logic. For more information, see Amazon S3 Path Deprecation Plan on the AWS News Blog.

Path-style requests

Currently, Amazon S3 supports both virtual-hosted–style and path-style URL access in all AWS Regions. However, path-style URLs will be discontinued in the future. For more information, see the following Important note.

In Amazon S3, path-style URLs use the following format:

https://s3.region-code.amazonaws.com/bucket-name/key-name

For example, if you create a bucket named DOC-EXAMPLE-BUCKET1 in the US West (Oregon) Region, and you want to access the puppy.jpg object in that bucket, you can use the following path-style URL:

https://s3.us-west-2.amazonaws.com/DOC-EXAMPLE-BUCKET1/puppy.jpg
Important

Update (September 23, 2020) – To make sure that customers have the time that they need to transition to virtual-hosted–style URLs, we have decided to delay the deprecation of path-style URLs. For more information, see Amazon S3 Path Deprecation Plan – The Rest of the Story in the AWS News Blog.

Virtual-hosted–style requests

In a virtual-hosted–style URI, the bucket name is part of the domain name in the URL.

Amazon S3 virtual-hosted–style URLs use the following format:

https://bucket-name.s3.region-code.amazonaws.com/key-name

In this example, DOC-EXAMPLE-BUCKET1 is the bucket name, US West (Oregon) is the Region, and puppy.png is the key name:

https://DOC-EXAMPLE-BUCKET1.s3.us-west-2.amazonaws.com/puppy.png

HTTP Host header bucket specification

As long as your GET request does not use the SSL endpoint, you can specify the bucket for the request by using the HTTP Host header. The Host header in a REST request is interpreted as follows:

  • If the Host header is omitted or its value is s3.region-code.amazonaws.com, the bucket for the request will be the first slash-delimited component of the Request-URI, and the key for the request will be the rest of the Request-URI. This is the ordinary method, as illustrated by the first and second examples in this section. Omitting the Host header is valid only for HTTP 1.0 requests.

  • Otherwise, if the value of the Host header ends in .s3.region-code.amazonaws.com, the bucket name is the leading component of the Host header's value up to .s3.region-code.amazonaws.com. The key for the request is the Request-URI. This interpretation exposes buckets as subdomains of .s3.region-code.amazonaws.com, as illustrated by the third and fourth examples in this section.

  • Otherwise, the bucket for the request is the lowercase value of the Host header, and the key for the request is the Request-URI. This interpretation is useful when you have registered the same DNS name as your bucket name and have configured that name to be a canonical name (CNAME) alias for Amazon S3. The procedure for registering domain names and configuring CNAME DNS records is beyond the scope of this guide, but the result is illustrated by the final example in this section.

Examples

This section provides example URLs and requests.

Example – Path-style URLs and requests

This example uses the following:

  • Bucket Name ‐ example.com

  • Region ‐ US East (N. Virginia)

  • Key Name ‐ homepage.html

The URL is as follows:

http://s3.us-east-1.amazonaws.com/example.com/homepage.html

The request is as follows:

GET /example.com/homepage.html HTTP/1.1 Host: s3.us-east-1.amazonaws.com

The request with HTTP 1.0 and omitting the Host header is as follows:

GET /example.com/homepage.html HTTP/1.0

For information about DNS-compatible names, see Limitations. For more information about keys, see Keys.

Example – Virtual-hosted–style URLs and requests

This example uses the following:

  • Bucket nameDOC-EXAMPLE-BUCKET1.eu

  • Region ‐ Europe (Ireland)

  • Key namehomepage.html

The URL is as follows:

http://DOC-EXAMPLE-BUCKET1.eu.s3.eu-west-1.amazonaws.com/homepage.html

The request is as follows:

GET /homepage.html HTTP/1.1 Host: DOC-EXAMPLE-BUCKET1.eu.s3.eu-west-1.amazonaws.com

Example – CNAME alias method

To use this method, you must configure your DNS name as a CNAME alias for bucket-name.s3.us-east-1.amazonaws.com. For more information, see Customizing Amazon S3 URLs with CNAME records.

This example uses the following:

  • Bucket Name ‐ example.com

  • Key namehomepage.html

The URL is as follows:

http://www.example.com/homepage.html

The example is as follows:

GET /homepage.html HTTP/1.1 Host: www.example.com

Customizing Amazon S3 URLs with CNAME records

Depending on your needs, you might not want s3.region-code.amazonaws.com to appear on your website or service. For example, if you're hosting website images on Amazon S3, you might prefer http://images.example.com/ instead of http://images.example.com.s3.us-east-1.amazonaws.com/. Any bucket with a DNS-compatible name can be referenced as follows: http://BucketName.s3.Region.amazonaws.com/[Filename], for example, http://images.example.com.s3.us-east-1.amazonaws.com/mydog.jpg. By using CNAME, you can map images.example.com to an Amazon S3 hostname so that the previous URL could become http://images.example.com/mydog.jpg.

Your bucket name must be the same as the CNAME. For example, if you create a CNAME to map images.example.com to images.example.com.s3.us-east-1.amazonaws.com, both http://images.example.com/filename and http://images.example.com.s3.us-east-1.amazonaws.com/filename will be the same.

The CNAME DNS record should alias your domain name to the appropriate virtual hosted–style hostname. For example, if your bucket name and domain name are images.example.com and your bucket is in the US East (N. Virginia) Region, the CNAME record should alias to images.example.com.s3.us-east-1.amazonaws.com.

images.example.com CNAME images.example.com.s3.us-east-1.amazonaws.com.

Amazon S3 uses the hostname to determine the bucket name. So the CNAME and the bucket name must be the same. For example, suppose that you have configured www.example.com as a CNAME for www.example.com.s3.us-east-1.amazonaws.com. When you access http://www.example.com, Amazon S3 receives a request similar to the following:

GET / HTTP/1.1 Host: www.example.com Date: date Authorization: signatureValue

Amazon S3 sees only the original hostname www.example.com and is unaware of the CNAME mapping used to resolve the request.

You can use any Amazon S3 endpoint in a CNAME alias. For example, s3.ap-southeast-1.amazonaws.com can be used in CNAME aliases. For more information about endpoints, see Request Endpoints. To create a static website by using a custom domain, see Configuring a static website using a custom domain registered with Route 53.

Important

When using custom URLs with CNAMEs, you will need to ensure a matching bucket exists for any CNAME or alias record you configure. For example, if you create DNS entries for www.example.com and login.example.com to publish web content using S3, you will need to create both buckets www.example.com and login.example.com.

When a CNAME or alias records is configured pointing to an S3 endpoint without a matching bucket, any AWS user can create that bucket and publish content under the configured alias, even if ownership is not the same.

For the same reason, we recommend that you change or remove the corresponding CNAME or alias when deleting a bucket.

How to associate a hostname with an Amazon S3 bucket

To associate a hostname with an Amazon S3 bucket by using a CNAME alias

  1. Select a hostname that belongs to a domain that you control.

    This example uses the images subdomain of the example.com domain.

  2. Create a bucket that matches the hostname.

    In this example, the host and bucket names are images.example.com. The bucket name must exactly match the hostname.

  3. Create a CNAME DNS record that defines the hostname as an alias for the Amazon S3 bucket.

    For example:

    images.example.com CNAME images.example.com.s3.us-west-2.amazonaws.com

    Important

    For request-routing reasons, the CNAME DNS record must be defined exactly as shown in the preceding example. Otherwise, it might appear to operate correctly, but it will eventually result in unpredictable behavior.

    The procedure for configuring CNAME DNS records depends on your DNS server or DNS provider. For specific information, see your server documentation or contact your provider.

Limitations

SOAP support over HTTP is deprecated, but SOAP is still available over HTTPS. New Amazon S3 features are not supported for SOAP. Instead of using SOAP, we recommend that you use either the REST API or the AWS SDKs.

Backward compatibility

The following sections cover various aspects of Amazon S3 backward compatibility that relate to path-style and virtual-hosted–style URL requests.

Legacy endpoints

Some Regions support legacy endpoints. You might see these endpoints in your server access logs or AWS CloudTrail logs. For more information, review the following information. For a complete list of Amazon S3 Regions and endpoints, see Amazon S3 endpoints and quotas in the Amazon Web Services General Reference.

Important

Although you might see legacy endpoints in your logs, we recommend that you always use the standard endpoint syntax to access your buckets.

Amazon S3 virtual-hosted–style URLs use the following format:

https://bucket-name.s3.region-code.amazonaws.com/key-name

In Amazon S3, path-style URLs use the following format:

https://s3.region-code.amazonaws.com/bucket-name/key-name

s3‐Region

Some older Amazon S3 Regions support endpoints that contain a dash (-) between s3 and the Region code (for example, s3‐us-west-2), instead of a dot (for example, s3.us-west-2). If your bucket is in one of these Regions, you might see the following endpoint format in your server access logs or CloudTrail logs:

https://bucket-name.s3-region-code.amazonaws.com

In this example, the bucket name is DOC-EXAMPLE-BUCKET1 and the Region is US West (Oregon):

https://DOC-EXAMPLE-BUCKET1.s3-us-west-2.amazonaws.com

Legacy global endpoint

For some Regions, you can use the legacy global endpoint to construct requests that do not specify a Region-specific endpoint. The legacy global endpoint point is as follows:

bucket-name.s3.amazonaws.com

In your server access logs or CloudTrail logs, you might see requests that use the legacy global endpoint. In this example, the bucket name is DOC-EXAMPLE-BUCKET1 and the legacy global endpoint is:

https://DOC-EXAMPLE-BUCKET1.s3.amazonaws.com

Virtual-hosted–style requests for US East (N. Virginia)

Requests made with the legacy global endpoint go to the US East (N. Virginia) Region by default. Therefore, the legacy global endpoint is sometimes used in place of the Regional endpoint for US East (N. Virginia). If you create a bucket in US East (N. Virginia) and use the global endpoint, Amazon S3 routes your request to this Region by default.

Virtual-hosted–style requests for other Regions

The legacy global endpoint is also used for virtual-hosted–style requests in other supported Regions. If you create a bucket in a Region that was launched before March 20, 2019, and use the legacy global endpoint, Amazon S3 updates the DNS record to reroute the request to the correct location, which might take time. In the meantime, the default rule applies, and your virtual-hosted–style request goes to the US East (N. Virginia) Region. Amazon S3 then redirects it with an HTTP 307 Temporary Redirect to the correct Region.

For S3 buckets in Regions launched after March 20, 2019, the DNS server doesn't route your request directly to the AWS Region where your bucket resides. It returns an HTTP 400 Bad Request error instead. For more information, see Making requests.

Path-style requests

For the US East (N. Virginia) Region, you can use the legacy global endpoint for path-style requests.

For all other Regions, the path-style syntax requires that you use the Region-specific endpoint when attempting to access a bucket. If you try to access a bucket with the legacy global endpoint or another endpoint that is different than the one for the Region where the bucket resides, you receive an HTTP response code 307 Temporary Redirect error and a message that indicates the correct URI for your resource. For example, if you use https://s3.amazonaws.com/bucket-name for a bucket that was created in the US West (Oregon) Region, you will receive an HTTP 307 Temporary Redirect error.