Amazon S3 objects overview

The name that you assign to an object. You use the object key to retrieve the object. For more information, see Working with object metadata.

Within a bucket, a key and version ID uniquely identify an object. The version ID is a string that Amazon S3 generates when you add an object to a bucket. For more information, see Retaining multiple versions of objects with S3 Versioning.

The content that you are storing.

An object value can be any sequence of bytes. Objects can range in size from zero to 5 TB. For more information, see Uploading objects.

A set of name-value pairs with which you can store information regarding the object. You can assign metadata, referred to as user-defined metadata, to your objects in Amazon S3. Amazon S3 also assigns system-metadata to these objects, which it uses for managing objects. For more information, see Working with object metadata.

Amazon S3 uses the subresource mechanism to store object-specific additional information. Because subresources are subordinates to objects, they are always associated with some other entity such as an object or a bucket. For more information, see Object subresources.

You can control access to the objects you store in Amazon S3. Amazon S3 supports both the resource-based access control, such as an access control list (ACL) and bucket policies, and user-based access control. For more information about access control, see the following:

Your Amazon S3 resources (for example, buckets and objects) are private by default. You must explicitly grant permission for others to access these resources. For more information about sharing objects, see Sharing objects with presigned URLs.

You can use tags to categorize your stored objects, for access control, or cost allocation. For more information, see Categorizing your storage using tags.