Objects are placed in buckets and contain user data in whatever format it was uploaded in.

The object ID is the string key.

Along with the object, Object Storage stores user-defined and system metadata.

Object Storage allows you to store objects in standard and cold storage. For more information, see the section Storage class.

Object Storage supports the following operations with objects:

  • Uploading an object to storage
  • Downloading an object from storage.
  • Copying an object inside the storage (for example, from one bucket to another).

All other operations that can be performed using tools are combinations of the above.


Key is the ID of an object in a bucket.

The structure for storing objects is flat, but GUI-based tools allow you to work with Object Storage like a hierarchical file system. The hierarchical view is possible because keys can be written as paths in a file system (for example, top_level_prefix/subprefix/text_data.txt). In the Yandex.Cloud management console, prefixes are called folders.

A key must:

  • Be UTF-8 encoded.
  • Be less than 1024 bytes.
  • Not contain the characters : * ? " < > | !.

The following characters are safe to use in a key: [a-zA-Z0-9], -, _, /, \. Other characters may cause various problems when using Object Storage.


There are no folders in Object Storage, but GUI-based file management clients like CyberDuck or the interface to Object Storage simulate folders in the Yandex.Cloud management console. A zero-size object, whose key is included in the keys of other objects as a prefix, serves as a folder. For example, an object with an x key and zero size will be a folder in the management console, while an object with an x/y.txt key will be a y.txt object located in the x folder.

Each of the tools manages objects and folders according to their own logic described in their respective documentation.

The management console allows you to create folders and fill them with objects, but you can only delete an empty folder.


Metadata is stored with an object as name-value pairs.

Metadata can be system or user-defined.

System metadata

System metadata is defined by Object Storage.

Name Description
Date Date and time of sending a request to upload an object to Object Storage.
Content-Length Object size in bytes.
Last-Modified Date when the object was created or last modified.
Content-MD5 Object MD5 hash value, base64 encoded.

User-defined metadata

When uploading an object to Object Storage, you can pass a set of metadata as name-value pairs along with the object.

In the HTTP API compatible with Amazon S3, metadata is passed as HTTP headers. The header name must start with x-amz-meta-. When an object is requested via the HTTP API, Yandex Object Storage returns metadata in the form of HTTP headers with the same prefix.

Metadata names must conform to the HTTP header naming convention and be in lowercase.


The PUT request header must not exceed 8 KB. The maximum size of user-defined metadata in this header is 2 KB.