Cloud Object Storage

A secure and reliable massive cloud storage service at low cost


Cloud Object Storage (COS) is a distributed storage service launched by Tencent Cloud. It has no structure restrictions and is accessible via HTTP/HTTPS protocols. It can store massive amounts of data in buckets featuring unlimited storage space and no partition management requirements, making it especially suitable for a variety of use cases such as data delivery for CDN, data processing for CI, and data lake for big data computation and analysis. Moreover, it provides a web-based console, multilingual SDKs and APIs, as well as command line and graphical tools. It is readily compatible with AWS S3 APIs, allowing direct access to community tools and plugins with ease.


Stable and Durable

COS enables redundant storage of data across multiple architectures and devices and supports remote disaster recovery and resource isolation to provide up to 99.999999999% data persistence for each object, providing better data persistence than other storage architectures.

Secure and Reliable

Hotlink protection is supported to block malicious access. Data transmission can be encrypted with SSL technology to control the read/write permission of each file. Defense systems can effectively defend against DDoS and CC attacks to ensure your business operates normally.

Low Costs

There is no need for the traditional purchase, deployment and OPS, or to pay to reserve storage space in advance. The service is used as needed, and billed based on use. Lifecycle management can be used to identify cold data to further reduce costs.

Ease of Use

COS supports a variety of methods for conducting batch operations on storage objects such as graphical programs, command-line tools and protocol tools, further enhancing its ease of use. It also offers tools capable of mounting buckets to your local storage, enabling you to use COS just like a local file storage system.

Convenient Access

COS has a detailed RESTful API manual and a wide variety of SDK connection tools. There is also a seamless migration tool to quickly migrate your business into the cloud, helping you avoid high migration and connection costs.

Service Integration

COS can be integrated with other Tencent Cloud services, such as CDN, CI, audio/video transcoding, file preview and other components, to provide a fully integrated solution for storage and processing. In addition, it can be used as a data pool in big data computing to provide data sources for big data analysis and computation; it can also be connected to SCF to automate event notification and processing.


COS comes with a rich set of features such as checkpoint restart, custom object header, static website, and data migration. For more information, please see Feature Overview.
Object Management

1. Resume uploads from the breakpoint

If an upload is unexpectedly terminated, you can resume the upload from the breakpoint to reduce the time spent on repeated uploads.

2. Customize object headers

The object header is a string sent by a server before it sends HTML data to a browser via the HTTP protocol. You can change the response mode of a page or send configuration information by modifying the header. For example, the cache expiration time can be changed, but the file itself will not be changed.

3. Static websites

Static websites only contain static content (such as HTML) or client-side scripts. Users who don't need to display dynamic webpages can use COS to complete the whole process from storage to display. Users can host a static website by configuring a bucket (linked with a custom domain name) for the website on COS.

Storage Classes


Data persistence: 99.999999999%

Service availability: 99.95%

  • Use Cases: Trending videos, social networking photos, mobile apps, games, and dynamic websites.
  • Response: Within milliseconds
  • Supported regions: All
  • Storage cost: Standard


Data persistence: 99.999999999%

Service availability: 99.9%

  • Use Cases: Online file storage, big data analytics, governmental/organizational business data, low-frequency archives, and monitoring data
  • Minimum billing duration: 30 days
  • Minimum object size: 64 KB
  • First-byte delay: Within milliseconds
  • Supported regions: All
  • Storage cost: Low


Data persistence: 99.999999999%

Service availability: 99.99%

  • Use cases: scenarios where data access patterns are variable
  • Minimum billing duration: 30 days
  • Minimum object size: 64 KB
  • Response: within milliseconds
  • Supported regions: Beijing, Shanghai, Guangzhou, Chongqing, and Tokyo
  • Storage cost: same as that of the storage class after conversion


Data persistence: 99.999999999%

Service availability: 99.9%

  • Use cases: archive of compliance documents (e.g. archival data), lifecycle files, operational logs and remote disaster recovery
  • Minimum billing duration: 90 days
  • Minimum object size: 64 KB
  • Response: prior application for data restoration required
  • Supported regions: public cloud regions only
  • Storage cost: very low


Data persistence: 99.999999999%

Service availability: 99.9%

  • Use cases: medical image data, security surveillance data, and log data
  • Minimum billing duration: 180 days
  • Minimum object size: 64 KB
  • Response: prior application for data restoration required
  • Supported regions: Beijing, Shanghai, Guangzhou, and Chengdu
  • Storage cost: very low


Application Data Storage

COS provides SDKs in various languages according to the application type for seamless access, covering mobile apps, mobile websites and HTML5 pages. When business booms and the volume of user-generated content (UGC) soars up, COS scales automatically to meet requests and traffic demand in response to business access surges. As UGC access are usually time-specific, COS can separate hot and cold data and store the former in STANDARD storage class and the latter in STANDARD_IA storage class. COS automatically converts the storage class with lifecycle rule configuration, reducing the storage cost effectively.

Content Distribution

Web services generally separate frequently-changed resources from infrequently-changed resources in dynamic webpages according to a particular rule. Static resources refer to unstructured data resources that remain unchanged for a long time.

COS Standard allows static resources to be stored and distributed so as to relieve the pressure on resource servers. With infinite capacity and highly frequent read/write capabilities, the scalability and reliability of static resources are assured. Users can host the static content (including audio/video files and images) of a website in COS Standard and distribute content using Tencent Cloud CDN. Using the capacity of Tencent Cloud CDN global acceleration nodes, users can distribute hot files to edge nodes ahead of time to minimize access latency.

Big Data Analysis

COS can be used as a data source for big data analysis regardless of the type of data (medical or financial data, or multimedia files such as images, audio and video).

COS supports the storage of exabytes of unconstructed data, providing high availability, high reliability, high security and high scalability. Analysis apps can be rapidly built and deployed using the Tencent Cloud Big Data Suite. After your high performance computing need is met, you can archive the data to reduce service costs and store the data long term.

Disaster Recovery and Backup

Data uploaded to COS can be stored in multiple designated regions simultaneously by utilizing cross-regional duplication, ensuring that redundant data can be used to find and recover complete sets of data in a situation of accidental loss of partial data. In addition, by virtue of storing data across different regions, data loss caused by unavoidable disasters in one region can be circumvented, making multi-redundancy backup and cross-regional disaster recovery possible and ensuring data persistence and stability with yet another layer of security.


COS fees are broken down into five categories: storage, requests, data retrievals, traffic, and management features. Traffic fees, DEEP_ARCHIVE data retrieval fees, and management feature fees are on a daily billing cycle, where the fees for the day are calculated and billed on the following day. The remaining billable items are on a monthly billing cycle, where the fees for the month are calculated and billed on the 3rd to 5th day of the following month. Your can view your bills in the Tencent Cloud Console. See Viewing Billing Details for more information. Please refer to COS Pricing for the fee of COS.