Cross-region and cross-border transfers suffer from high latency and unstable throughput on the public internet. Transfer acceleration routes requests through Alibaba Cloud's global access points and internal backbone network, providing a faster and more reliable path for uploads and downloads without changing your bucket or objects.
When to use transfer acceleration
Transfer acceleration is most effective when:
Users or services upload to a centralized bucket from multiple geographic locations worldwide
Your application serves a global audience and download latency is noticeable
You regularly transfer large files (gigabytes to terabytes) across regions or across borders
Public internet congestion or instability is degrading transfer reliability
How it works
When a request hits the acceleration endpoint, OSS routes it to the nearest Alibaba Cloud access point. From there, the data travels over Alibaba Cloud's internal backbone network—bypassing the public internet—directly to the region where your bucket resides.
For example, a user in Beijing accessing a bucket in Chengdu through the standard public endpoint traverses multiple public internet hops. With transfer acceleration, the request enters Alibaba Cloud's network at a local access point in Beijing, then travels via the internal backbone to Chengdu. This reduces public internet exposure and improves both speed and stability.
Transfer acceleration optimizes the transmission path but cannot eliminate the effects of ISP link quality or cross-border network congestion. Actual performance depends on your users' location, ISP conditions, and network state at the time of transfer.
Enable transfer acceleration
Before you begin, ensure that you have:
An existing OSS bucket
Permission to modify bucket settings in the OSS console
Steps:
Go to the Buckets page and click the target bucket.
In the left navigation pane, click Bucket Settings > Transfer Acceleration.
Click the toggle next to Transfer Acceleration, then click OK in the confirmation dialog box.
It takes about 30 minutes for the change to take effect globally. Wait until propagation completes before running verification tests. Your existing public endpoints remain fully functional during and after this period.
Access OSS through the acceleration endpoint
To use transfer acceleration, replace the endpoint in your requests with the acceleration endpoint. Your original public endpoints continue to work—acceleration applies only to requests that use the acceleration endpoint.
Choose an acceleration endpoint
| Scenario | Endpoint | Notes |
|---|---|---|
| General (default) | oss-accelerate.aliyuncs.com | Works for all regions |
| Custom domain without ICP filing via CNAME | oss-accelerate-overseas.aliyuncs.com | Domains without ICP filing cannot resolve to IP addresses in the Chinese mainland; point your CNAME to this endpoint instead |
When configuring SDKs, ossutil, ossbrowser, or other tools, set the endpoint to oss-accelerate.aliyuncs.com. Do not include the bucket name. Configuring the endpoint as <BucketName>.oss-accelerate.aliyuncs.com causes domain resolution failures.
Public-read and public-read-write buckets
Access objects directly by URL:
https://example-bucket.oss-accelerate.aliyuncs.com/example.jpgReplace example-bucket with your bucket name and example.jpg with your object key.
Private buckets
Private bucket requests require a signed URL. To get one from the console:
Go to the Buckets page and click the target bucket.
In the Actions column for the target object, click Details.
Click Copy Object URL.
In the copied URL, replace the public endpoint (for example,
oss-cn-hangzhou.aliyuncs.com) withoss-accelerate.aliyuncs.com.
For programmatic signed URL generation, see Signature Version 4 (recommended).
Verify acceleration performance
The following test compares download speeds from a bucket in the China (Hangzhou) region to an ECS instance in the Japan (Tokyo) region using ossutil. It downloads an ~8.85 MiB file under each configuration.
Without acceleration (public endpoint):
ossutil cp oss://example-bucket/ossutil-2.1.2-mac-arm64.zip ossutil-2.1.2-mac-arm64.zip \
-e oss-cn-hangzhou.aliyuncs.comOutput:
Success: Total 1 object, size 9281195 B, Download done:(1 files, 9281195 B), avg 8.733 MiB/s
1.013983(s) elapsedWith acceleration (acceleration endpoint):
ossutil cp oss://example-bucket/ossutil-2.1.2-mac-arm64.zip ossutil-2.1.2-mac-arm64.zip \
-e oss-accelerate.aliyuncs.comOutput:
Success: Total 1 object, size 9281195 B, Download done:(1 files, 9281195 B), avg 20.155 MiB/s
0.440160(s) elapsedIn this test, transfer acceleration reduced download time from ~1.01 s to ~0.44 s (2.3x faster).
Apply in production
Best practices
Combine CDN with transfer acceleration
Point your CDN origin to oss-accelerate.aliyuncs.com to build a two-layer architecture: CDN edge caching handles cache hits, while transfer acceleration optimizes the CDN's origin fetch path. This is ideal for globally distributed static resources and delivers full-path optimization for both cache hits and origin fetches. See CDN acceleration.
Use multipart operations for large files
For gigabyte- to terabyte-scale transfers, combine transfer acceleration with multipart upload and resumable download. Transfer acceleration improves network path quality; multipart operations increase concurrency and fault tolerance. Together they reduce timeout risk and improve overall throughput.
Apply endpoint selection by user group
For users in the same region or with good network conditions, use the public endpoint to avoid acceleration charges. For cross-region or cross-border users, switch to the acceleration endpoint. Build your endpoint strategy based on user geography, business priority, and cost budget.
Fault tolerance
Implement an endpoint fallback mechanism
If the acceleration endpoint becomes unavailable, your application should automatically fall back to the public endpoint. Transfer acceleration and the public endpoint operate independently—a failure in one does not affect the other. Implement retry logic with exponential backoff and automatic endpoint fallback to maintain business continuity.
Limitations
| Limitation | Description |
|---|---|
| Protocol support | HTTP and HTTPS only. Non-HTTP/HTTPS protocols such as RTMP are not supported. |
| Propagation time | Enabling or disabling transfer acceleration takes about 30 minutes to take effect globally. |
| Access mode | Supports only third-level domain access (bucket name included in the hostname). Cannot be used for bucket management operations such as listing buckets. Use the public endpoint for management operations. |
| Secure transmission | The backend may use HTTPS for internal data transmission. If a client accesses data over HTTP, the access log may still show HTTPS. |
Billing
Enabling transfer acceleration is free. Charges apply for accelerated upload traffic and accelerated download traffic when you access OSS through the acceleration endpoint. These fees are billed separately from standard public internet outbound traffic fees.
| Access method | Charges |
|---|---|
| Acceleration endpoint | Accelerated traffic fees + public internet outbound fees |
| Public endpoint | Public internet outbound fees only |
For pricing details, see Transfer acceleration fees.
FAQ
Why am I getting 502 or 504 errors from the acceleration endpoint?
This is expected behavior. Transfer acceleration uses an automatic path-switching mechanism to handle network fluctuations and changing link quality during long-distance transfers. During a path switch, a small number of in-flight requests may be interrupted and return 502 or 504. Implement exponential backoff retry logic in your client code to handle these transient failures.
I enabled transfer acceleration, but downloads are not faster. Why?
Enabling the feature alone is not enough—you also need to change the endpoint in your requests to oss-accelerate.aliyuncs.com. If your code or tools still use the standard public endpoint, acceleration does not apply.
I'm getting errors right after enabling transfer acceleration. What's wrong?
It takes about 30 minutes for transfer acceleration to propagate globally. Requests made to the acceleration endpoint before propagation completes may fail. Wait and retry after 30 minutes.
Cross-border access is still slow even with the acceleration endpoint. What should I check?
Transfer acceleration improves the transmission path but cannot compensate for ISP-level cross-border congestion. Check the following:
Confirm the endpoint is set to
oss-accelerate.aliyuncs.com, with no bucket name in the endpoint value.For large files, add multipart upload and resumable download to improve reliability under poor network conditions.
Add an endpoint fallback in your application to switch to the public endpoint when the acceleration endpoint becomes unstable.
How is transfer acceleration billed? Is it on top of regular traffic fees?
Yes, the fees are separate. Using the acceleration endpoint incurs both accelerated traffic fees and public internet outbound fees. Using the standard public endpoint incurs only public internet outbound fees—no acceleration charge. Enabling the feature itself is free; charges apply only when data flows through the acceleration endpoint.