Object Storage Service:How do I troubleshoot object upload and download failures in OSS?

1. Check network connectivity

Run ping against your OSS endpoint to confirm the local client can reach OSS. Fix any network issues before proceeding.

2. Check the object size limit

The maximum object size depends on the upload method:

If your object exceeds 5 GB, switch to multipart upload. See How do I upload large objects to OSS?

3. Check permissions

If you are uploading as a Resource Access Management (RAM) user, verify the user has upload permissions on the target bucket:

1. Log on to the RAM console. In the left-side navigation pane, choose Identities > Users, then click the RAM user's name.

2. Click the Permissions tab and confirm the user has upload permissions on the bucket or object.

If the RAM user lacks the required permissions, ask your administrator to grant them. See Configure bucket policies to authorize other users to access OSS resources.

4. Check your upload configuration

If you are using an OSS SDK, verify these settings:

• Endpoint: Make sure the endpoint matches the region where the bucket is located. For example, a bucket in the China (Hangzhou) region uses the public endpoint oss-cn-hangzhou.aliyuncs.com. For all endpoints, see OSS domain names.

  Note: To access buckets in multiple regions, create a separate OSSClient instance for each region, each with its own regional endpoint. For endpoints by region and network type, see Access OSS via a bucket domain name.

• AccessKey ID and AccessKey secret: Confirm both values in your code are correct.

• Bucket name and object name: Confirm both names are valid:

  Resource	Rules
  Bucket name	3–63 characters; lowercase letters, digits, and hyphens (-) only; must start and end with a lowercase letter or digit
  Object name	1–1,023 bytes; UTF-8 encoded; cannot start with / or \

  For full naming rules, see Terms.

If you are using an OSS tool, check the tool's supported scenarios and limits in OSS tools. ossutil is the recommended tool for most upload scenarios. See ossutil overview.

5. Consult issue-specific guides

If the steps above do not resolve the issue, see the relevant guide:

• What do I do if the speed is slow when I upload objects to or download objects from OSS?

• How do I fix the "Image has no exif info" error reported for an EXIF information query?

• What do I do if the "Connect to oss failed: \[Errno -2\] Name or service not known" error appears?

• What do I do if an object uploaded to OSS via MemoryStream in OSS SDK for .NET has a size of zero?

• How do I troubleshoot upload callback errors?

• What do I do if OSS returns the "OSS Transfer Acceleration is not configured on this bucket" error?

1. Check network connectivity

Run ping against your OSS endpoint. Fix any network issues before proceeding.

2. Check the download limit

The OSS console supports downloading up to 100 objects at a time. To download more objects, use ossutil or ossbrowser.

3. Check permissions and configuration

Follow the same steps as Check permissions and Check your upload configuration above.

4. Use resumable download

For large objects or unreliable network conditions, use a tool that supports resumable download:

• ossutil with the cp command

• ossbrowser

5. Consult issue-specific guides

• What do I do if a downloaded object is not the latest version?

• What do I do if a RAR file downloaded from OSS contains garbled characters?

• What do I do if the downloaded content differs from the actual content?