Objects are basic units stored in OBS. An object contains both data and the metadata that describes data attributes. Data uploaded to OBS is stored in buckets as objects.

An object consists of the following:

A key that specifies the name of an object. An object key is a UTF-8 string up to 1,024 characters long. Each object is uniquely identified by a key within a bucket.
Metadata that describes an object. The metadata is a set of key-value pairs that are assigned to objects stored in OBS. There are two types of metadata: system-defined metadata and custom metadata.
- System-defined metadata is automatically assigned by OBS for processing objects. Such metadata includes Date, Content-Length, Last-Modified, ETag, and more.
- You can specify custom metadata to describe the object when you upload an object to OBS.
Data that refers to the content of an object.

Generally, objects are managed as files. However, OBS is an object-based storage service and there is no concept of files and folders. For easy data management, OBS provides a method to simulate folders. By adding a slash (/) to an object name, for example, test/123.jpg, you can specify test as a folder and 123.jpg as the name of a file in the test folder. The key of the object is test/123.jpg.

When uploading an object, you can set a storage class for the object. If no storage class is specified, the object is stored in the same storage class as the bucket in which it resides. You can also change the storage class of an existing object in a bucket.

On OBS Console and OBS Browser+, you can use folders the same way you use them in a file system.