Object Storage Service (OSS) is a secure, low-cost, and highly durable cloud storage service from Alibaba Cloud that offers unlimited capacity. OSS delivers 99.9999999999% (twelve 9s) data durability and 99.995% service availability, backed by a RESTful API that lets any application store and retrieve data from anywhere.
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Storage classes
OSS offers five storage classes covering the full spectrum from frequently accessed data to long-term archival. Choose based on how often you access your data and how quickly you need it back.
| Storage class | Recommended for | Min. billable size | Min. storage duration | Retrieval |
|---|---|---|---|---|
| Standard (recommended for most workloads) | Frequently accessed data — social apps, image/video sharing, big data analytics | — | — | Immediate |
| IA (Infrequent Access) | Data accessed once or twice a month | 64 KB | 30 days | Immediate (retrieval fees apply) |
| Archive | Rarely accessed data — archival records, medical images, video footage | 64 KB | 60 days | ~1 minute to restore, or immediate if real-time access is enabled |
| Cold Archive | Cold data retained for compliance, big data/AI raw data, film and TV media | 64 KB | 180 days | Varies by size and priority (retrieval + API fees apply) |
| Deep Cold Archive | Extremely cold data kept for the longest periods — regulatory documents, tape-equivalent archival | 64 KB | 180 days | Varies by size and priority (retrieval + API fees apply) |
Start with Standard for most workloads. Move to IA, Archive, Cold Archive, or Deep Cold Archive as your data cools and cost savings become the priority.
For a full comparison of storage class pricing and restore behavior, see Storage classes.
Use cases
OSS is designed for:
Serving images, audio, and video directly to users. Every object in OSS has a unique HTTP URL. OSS also integrates with Alibaba Cloud CDN to publish content to edge nodes, reducing latency for end users globally.
Hosting static websites. Store HTML, JavaScript, images, and video at low cost, with no server to manage.
Storing data for distributed compute and analytics. OSS scales horizontally — multiple compute nodes can read and write concurrently without the bottlenecks of single-node storage.
Backing up and archiving data. Set lifecycle rules to automatically transition aging data to lower-cost storage classes. Use cross-region replication to maintain copies in a separate region for disaster recovery.
Performance
Proximity: Data access between an Elastic Compute Service (ECS) instance and an OSS bucket is fastest when both are in the same region. Server-side latency is negligible relative to network latency.
Large file uploads: For files over 5 GB, use multipart upload. OSS splits the object into parts, uploads them separately, and assembles the final object after all parts succeed. If a part fails, retry only that part — not the entire upload.
Long-distance transfers: Transfer acceleration uses a global network of optimized transmission links, a tuned protocol stack, and smart scheduling to accelerate both uploads and downloads over long distances. This feature also covers dynamic content and non-hotspot file downloads.
Download acceleration for static content: For hot static files, integrate Alibaba Cloud CDN with OSS. CDN caches content at edge nodes and routes user requests to the nearest node, reducing load on your origin bucket and improving response times.
Metadata queries: Many applications pair OSS with a search engine (such as OpenSearch) or a database (such as Tablestore or ApsaraDB RDS). OSS stores the objects; the search engine or database indexes metadata such as file names, sizes, and keywords. This lets you run precise queries and retrieve the matching objects from OSS.
Data durability and availability
OSS uses a data redundancy mechanism that replicates data across multiple Availability Zones (AZs) within the same region. If one AZ becomes unavailable, data access continues uninterrupted. For three-AZ deployments, OSS provides:
99.9999999999% (twelve 9s) data durability
99.995% service availability
OSS also automatically stores replicas of your data on different servers within the same region, ensuring high extensibility and elasticity. The total storage capacity of OSS and the capacity of a single bucket are unlimited — you can store an unlimited number of objects in a bucket.
To protect against regional failures, enable cross-region replication. After enabling it, OSS automatically and asynchronously replicates objects to a bucket in a different region in near real time. Both the source and destination buckets maintain the same twelve-9s durability and 99.995% availability guarantees.
Security
OSS provides layered security controls:
Encryption: Server-side encryption and client-based encryption protect data at rest and in transit.
Access control: Fine-grained permission control and hotlink protection whitelists restrict who can read or write your data.
Auditing: Log audit captures a complete record of access and modification events.
Compliance: Retention policies prevent objects from being deleted or overwritten for a specified period. OSS is the only cloud service in the Chinese mainland audited and certified by Cohasset Associates, meeting the electronic record retention requirements of SEC Rule 17a-4(f), FINRA 4511, and CFTC 1.31.
For a complete overview of security capabilities, see the OSS Security and Compliance Whitepaper.
Access methods
OSS exposes a standard RESTful API. Buckets act as top-level containers with globally unique names. Each object is identified by an object key — its unique name within the bucket. OSS has no native folder hierarchy, but you can simulate directories by using / as a delimiter in object keys (for example, logs/2026/03/access.log).
| Tool | Type | Best for |
|---|---|---|
| OSS API | RESTful API | Direct integration; supports Java, Python, PHP, Go, Android, iOS, and 10+ other languages via SDKs |
| ossutilGraphical management tool ossbrowser 1.0 | Command-line interface | Scripting and automation; supports ls, cp, cat, and config; runs on Windows, Linux, and Mac |
| ossbrowser 1.0 | Desktop GUI | Visually browsing, uploading, and downloading files and folders |
| OSS console | Web console | Managing OSS resources from a browser without writing code |
To receive notifications when objects are created, modified, or deleted, configure event notifications.
Billing
OSS fees consist of four components: storage, traffic, requests, and data processing.
By default, billing is pay-as-you-go: actual usage x unit price, calculated and charged hourly based on the previous hour's consumption. For predictable workloads, purchase a subscription resource plan in advance and usage is deducted from the plan quota.
For a complete list of billable items and pricing, see Billable items.