Naming Amazon S3 objects - Amazon Simple Storage Service (original) (raw)

The object key (or key name) uniquely identifies the object in an Amazon S3 bucket. When you create an object, you specify the key name. For example, on the Amazon S3 console, when you select a bucket, a list of objects in your bucket appears. These names are the object keys.

The object key name is a sequence of Unicode characters with UTF-8 encoding of up to 1,024 bytes long, or 1,204 Latin characters. In some locales, a single character can equal 2 bytes. When naming your objects, be aware of the following:

Choosing object key names

The Amazon S3 data model is a flat structure: You create a bucket, and the bucket stores objects. There is no hierarchy of subbuckets or subfolders. However, you can infer logical hierarchy using key name prefixes and delimiters as the Amazon S3 console does. The Amazon S3 console supports a concept of folders. For more information about how to edit metadata from the Amazon S3 console, see Editing object metadata in the Amazon S3 console.

Suppose that your bucket (admin-created) has four objects with the following object keys:

Development/Projects.xls

Finance/statement1.pdf

Private/taxdocument.pdf

s3-dg.pdf

The console uses the key name prefixes (Development/,Finance/, and Private/) and delimiter (/) to present a folder structure. The s3-dg.pdf key doesn't contain a slash-delimited prefix, so its object appears directly at the root level of the bucket. If you open the Development/ folder, you see theProjects.xlsx object in it.

Object key naming guidelines

You can use any UTF-8 character in an object key name. However, using certain characters in key names can cause problems with some applications and protocols. The following guidelines help you maximize compliance with DNS, web-safe characters, XML parsers, and other APIs.

Safe characters

The following character sets are generally safe for use in key names:

Alphanumeric characters 0-9 a-z A-Z
Special characters Exclamation point (!) Hyphen (-) Underscore (_) Period (.) Asterisk (*) Single quotation mark (') Opening parenthesis (() Closing parenthesis ())

The following are examples of valid object key names:

Note

If you use the Amazon S3 console to download objects that have key names that end with periods (.), the periods are removed from the ends of the key names of the downloaded objects. To retain periods at the ends of key names in downloaded objects, you must use the AWS Command Line Interface (AWS CLI), AWS SDKs, or Amazon S3 REST API.

In addition, be aware of the following prefix limitations:

Characters that might require special handling

The following characters in a key name might require additional code handling and most likely must be URL encoded or referenced as HEX. Some of these characters are non-printable characters that your browser might not handle, which also require special handling:

Characters to avoid

We recommend not using the following characters in a key name because of significant special character handling, which isn't consistent across all applications:

As specified by the XML standard on end-of-line handling, all XML text is normalized such that single carriage returns (ASCII code 13) and carriage returns immediately followed by a line feed (ASCII code 10), also known as newline characters, are replaced by a single line feed character. To ensure the correct parsing of object keys in XML requests, carriage returns and other special characters must be replaced with their equivalent XML entity code when they're inserted within XML tags.

The following is a list of such special characters and their equivalent XML entity codes:

The following example illustrates the use of an XML entity code as a substitution for a carriage return. This DeleteObjects request deletes an object with the key parameter/some/prefix/objectwith\rcarriagereturn (where the\r is the carriage return).

<Delete xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
  <Object>
    <Key>/some/prefix/objectwith&#13;carriagereturn</Key>
  </Object>
</Delete>