This page lists hard limits and reference quotas for Object Storage Service (OSS). Hard limits are enforced and cannot be exceeded. Reference quotas are high-end targets — actual performance depends on object size, access patterns, and workload characteristics.
Bandwidth
The following table lists the maximum bandwidth per Alibaba Cloud account in each region.
Public download and upload bandwidth limits apply to internet traffic only. Internal (intranet) traffic counts toward the total bandwidth but has no separate limit unless stated.
| Region | Total download bandwidth | Public download bandwidth | Total upload bandwidth | Public upload bandwidth |
|---|---|---|---|---|
| China (Shanghai) | 100 Gbps | 10 Gbps | 20 Gbps | 10 Gbps |
| China (Shenzhen) | 100 Gbps | 10 Gbps | 20 Gbps | 10 Gbps |
| China (Beijing) | 100 Gbps | 10 Gbps | 20 Gbps | 10 Gbps |
| China (Hangzhou) | 100 Gbps | 20 Gbps | 20 Gbps | 20 Gbps |
| Singapore | 100 Gbps | 5 Gbps | 20 Gbps | 5 Gbps |
| China (Zhangjiakou) | 20 Gbps | Constrained by total download bandwidth | 20 Gbps | Constrained by total upload bandwidth |
| China (Wuhan - Local Region) | 2 Gbps | Constrained by total download bandwidth | 2 Gbps | Constrained by total upload bandwidth |
| South Korea (Seoul) | 2 Gbps | Constrained by total download bandwidth | 2 Gbps | Constrained by total upload bandwidth |
| Thailand (Bangkok) | 2 Gbps | Constrained by total download bandwidth | 2 Gbps | Constrained by total upload bandwidth |
| China (Nanjing - Local Region) (Closing Down) | 2 Gbps | Constrained by total download bandwidth | 2 Gbps | Constrained by total upload bandwidth |
| China (Fuzhou - Local Region) (Closing Down) | 2 Gbps | Constrained by total download bandwidth | 2 Gbps | Constrained by total upload bandwidth |
| Other regions in the Chinese mainland | 10 Gbps | Constrained by total download bandwidth | 10 Gbps | Constrained by total upload bandwidth |
| Other regions outside the Chinese mainland | 5 Gbps | Constrained by total download bandwidth | 5 Gbps | Constrained by total upload bandwidth |
When the bandwidth limit is reached, OSS throttles requests and includes x-oss-qos-delay-time: number in the response header, where number is the throttling duration in milliseconds. For upload requests, the value is the exact throttling duration. For download requests, it is an estimated duration based on throttling level and object size.
Background operations — including lifecycle rules, cross-region replication, Same-region replication (SRR), and last access time updates — do not count toward your account's QPS or bandwidth quotas. Only read, write, and delete operations initiated with temporary credentials from AssumeRole are counted. Cross-region replication has its own separate QPS quota independent of your account quota.
Queries per second (QPS)
A single Alibaba Cloud account supports up to 10,000 queries per second (QPS). The effective limit depends on the read/write pattern:
| Read/write mode | QPS |
|---|---|
| Sequential read/write | 2,000 |
| Non-sequential read/write | 10,000 |
Single-file uploads and downloads are subject to a combined QPS limit of 2,000 and a peak bandwidth of 10 Gbps, in addition to the account-level and bucket-level limits above.
Avoiding sequential-prefix performance degradation
If many objects share a sequential prefix (such as a timestamp or alphabetical sequence), their indexes concentrate in a single partition, which can degrade performance under high request rates. Use random prefixes for object names when uploading at scale. For guidance on converting sequential prefixes to random ones, see OSS performance best practices.
Buckets
An account can have up to 100 buckets per region. To request a higher quota, submit a request in Quota Center.
Bucket names must be globally unique within OSS. See Bucket naming conventions.
After a bucket is created, its name, region, and storage class cannot be changed.
There is no capacity limit on a single bucket.
Objects
Upload size limits
| Upload method | Maximum object size |
|---|---|
| Simple upload | 5 GB |
| Form upload | 5 GB |
| Append upload | 5 GB |
| Multipart upload | 48.8 TB |
For multipart upload details, see Multipart upload.
Rename limits
In the OSS console, only objects 1 GB or smaller can be renamed. To rename larger objects, use an SDK or the ossutil command-line tool. See Rename objects.
Batch delete limits
| Method | Maximum objects per operation |
|---|---|
| OSS console | 100 |
| SDK | 1,000 |
| ossutil | No limit |
| ossbrowser | No limit |
Deleted objects cannot be recovered. Proceed with caution.
Overwrite behavior
By default, uploading an object with the same name as an existing object overwrites it.
Overwritten objects cannot be recovered. To prevent accidental overwrites, enable versioning for the bucket, or include the x-oss-forbid-overwrite: true header in the upload request.
Restoring data
To access objects in Archive (when real-time access is not enabled), Cold Archive, or Deep Cold Archive storage, restore them first. Higher-priority restoration is faster but incurs higher data retrieval fees. See Data retrieval fees.
The restoration quotas below are reference targets. Requests exceeding these quotas are queued and may take longer than the stated time for the selected priority.
| Storage class | Priority | Restoration time | Reference restoration quota (per account per region) |
|---|---|---|---|
| Archive | — | Typically 1 minute | Not applicable |
| Cold Archive | Expedited | Within 1 hour | Average 500 objects/second; daily total 100 TB–120 TB across all priorities |
| Cold Archive | Standard | 2–5 hours | (Same quota as above) |
| Cold Archive | Bulk | 5–12 hours | (Same quota as above) |
| Deep Cold Archive | Expedited | Within 12 hours | Average 100 objects/second; daily total 10 TB–15 TB across both priorities |
| Deep Cold Archive | Standard | Within 48 hours | (Same quota as above) |
Domain name binding
Buckets in regions in the Chinese mainland require an ICP filing from the MIIT (Ministry of Industry and Information Technology). No filing is required for buckets in other regions.
A domain name can be bound to only one bucket.
A bucket can have up to 100 domain names bound to it.
There is no limit on the number of domain names per account.
Lifecycle rules
A bucket can have up to 1,000 lifecycle rules.
After a rule takes effect, lifecycle operations (object deletion, storage class transitions, and expiration of multipart upload parts) complete within 24 hours for the following capacity targets:
China (Hangzhou), China (Shanghai), China (Beijing), China (Zhangjiakou), China (Ulanqab), China (Shenzhen), and Singapore: up to 1 billion objects.
Other regions: up to 100 million objects.
Completion may take longer than 24 hours — in some cases, days or weeks — when there is a large object count, many tags, multiple versions per object, or a high volume of concurrent uploads.
With versioning enabled, each object version is counted as a separate operation.
Back-to-origin rules
A bucket can have up to 20 back-to-origin rules.
Default limits for mirroring-based back-to-origin:
| Region group | Default QPS | Default bandwidth |
|---|---|---|
| Chinese mainland and China (Hong Kong) | 2,000 | 2 Gbps |
| Other regions | 1,000 | 1 Gbps |
Image processing
Source image limits
| Attribute | Limit |
|---|---|
| Supported formats | JPG, PNG, BMP, GIF, WebP, TIFF, HEIC, AVIF |
| Maximum file size | 20 MB |
| Maximum dimensions (rotation) | 4,096 x 4,096 pixels |
| Maximum dimensions (other operations) | 30,000 pixels per side; 250 million pixels total |
| Pixel count (dynamic images, e.g., GIF) | Width x Height x Number of frames |
| Pixel count (static images) | Width x Height |
Scaled image limits
Neither dimension can exceed 16,384 pixels.
Total pixels cannot exceed 16,777,216.
Style limits
Each bucket supports up to 50 styles.
Processing capacity
| Region group | Throughput (by source image size) | QPS |
|---|---|---|
| China (Hangzhou), China (Shanghai), China (Beijing), China (Zhangjiakou), China (Shenzhen) | 20 MB/s | 50 |
| Other regions | 2 MB/s | 5 |
Resource plans
Region-specific resource plans offset fees only in the region where they are purchased. The region of a purchased plan cannot be changed.
Storage plans: multiple plans cannot be used concurrently, but you can upgrade an existing plan.
Transfer acceleration plans: multiple plans can be used concurrently, but cannot be upgraded or renewed.
Outbound data transfer plans and Anti-DDoS Basic plans: multiple plans can be used concurrently, but cannot be upgraded.
Request fees, Data processing fees, and Traffic fees for cross-region replication do not have a corresponding resource plan. These fees are billed on a pay-as-you-go basis only and do not support subscription.