Description
When you access a file in a browser using an OSS default domain name, the file might be downloaded directly instead of being previewed.
Cause
Starting from 10:00:00 on December 22, 2025, when you use an OSS default domain name to access specific file types in buckets created in the following regions, OSS adds two headers to the response:
The affected regions are:
China (Ulanqab)
China (Heyuan)
China (Guangzhou)
China (Nanjing - Local Region - Being Decommissioned)
Accessing files with the following Multipurpose Internet Mail Extensions (MIME) types triggers a forced download:
image/jpeg
image/gif
image/tiff
image/png
image/webp
image/svg+xml
image/bmp
image/x-ms-bmp
image/x-cmu-raster
image/exr
image/x-icon
image/heic
x-oss-force-download: true
Content-Disposition: attachmentWhen a standard browser encounters the Content-Disposition: attachment header, it prompts a download instead of displaying a preview.
Example
For example, you create a bucket in the China (Guangzhou) region and it contains a file named test.jpg. When you access test.jpg in a browser using the OSS default domain name:
GET /test.jpg HTTP/1.1Because the MIME type of test.jpg is image/jpeg, which is an affected file type, OSS adds the Content-Disposition and x-oss-force-download headers to the response.
HTTP/1.1 200 OK
Content-Disposition: attachment
x-oss-force-download: trueWhen a standard browser encounters the Content-Disposition: attachment header, it prompts a download instead of displaying a preview.
Solution
If you do not want OSS to return the force-download headers, access the object using a custom domain name. For more information, see Attach a custom domain name.