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Last Updated: Apr 14, 2021

Objects are the basic unit for data operations in OSS. Objects are also known as files. OSS does not use a hierarchical structure for objects, but instead uses a flat structure. All elements are stored as objects in buckets.

Object types

Objects can be classified into the following three types based on how they are created:

  • Normal: An object is generated by using Simple upload.

  • Multipart: An object is generated by using Multipart upload.

  • Appendable: An object is generated by using Append upload. You can append content only to objects of the Appendable type.

Object information

An object contains the following information:

  • Key: the name of the object. You can use the key of an object to query the object.

  • Data: the content stored in the object, which is a sequence of bytes.

  • Object metadata: the metadata of the object. Object metadata is a set of key-value pairs that define the attributes of the object, such as the last modified time and object size. You can add user metadata to the object metadata.

Object lifecycle

OSS provides the following object storage classes: Standard, Infrequent Access (IA), Archive, and Cold Archive. You can configure lifecycle rules to regularly delete expired objects and parts or convert the storage classes of non-hot objects to IA, Archive, or Cold Archive to save storage costs. For more information, see Lifecycle rules.

Authorized access

By default, the access control list (ACL) of buckets and objects is private. To allow unauthorized users to access these resources, you must configure the correct permissions on these resources. For example, if you store images and video objects of your website in OSS and want to allow unauthorized users to access these resources, you must set the ACL of these resources to public read. Otherwise, unauthorized users must use signed URLs to access these resources. For more information, see Authorize third-party users to download objects.