Docs

Torch Object Storage

Document preview

Overview

TOS allows you to preview documents stored in it in image, PDF, or HTML format. This topic covers billing notes, constraints, limitations, and ways to preview documents.

tip

This feature is currently in closed beta. Please contact your account manager for access.

Billing notes

You can preview documents in image, PDF, or HTML format. Billing varies by preview format. Specifically:

Preview format	Billing rules	Related documentation
Image or PDF	Costs are based on the number of images or PDF pages converted for preview.	Data processing
HTML	Costs are based on the number of previews.	Data processing

Data retrieval fees will apply when previewing documents stored in Infrequent Access Storage or Flashback Archive. These fees are calculated based on file size.

Constraints and limitations

Category	Description
File type	The following file types are supported for preview: Presentation files: PPTX and PPT. Word processing files: DOCX and DOC. Spreadsheet files: XLSX and XLS. Others: PDF.
Output format	The following output formats are supported: PNG, JPG, PDF, and HTML. warning Starting from October 18, 2022, for security and compliance reasons, if you use the bucket's default domain to access web page files with the MIME type text/html and extensions including .htm, .html, .jsp, .plg, .htx, and .stm, the response header will automatically include Content-Disposition:attachment. This means that, when you access web page files via a browser, the website will not preview the content directly. Instead, the content will be downloaded locally.
File size	The maximum size of a file that can be previewed is 200 MB.
Spreadsheet files	When you preview a spreadsheet file in image format, one sheet can be split into multiple images.
Server-side encryption	You can use TOS to preview documents encrypted with SSE-TOS, SSE-C, or SSE-KMS, but there are some limitations to consider: When previewing a document encrypted with SSE-C, you must include the following SSE-C request headers. For more information on SSE-C headers, see Using server-side encryption with customer-provided keys (SSE-C). x-tos-server-side-encryption-customer-algorithm x-tos-server-side-encryption-customer-key x-tos-server-side-encryption-customer-key-MD5 You cannot preview documents encrypted with SSE-KMS via anonymous access. To preview SSE-KMS-encrypted documents, you must activate Key Management Service (KMS) and have permission to access the master key. Requests must also be signed using valid credentials. You can use pre-signed URLs, APIs, or SDKs for this purpose. For more information, see the Using REST APIs section below.

Document preview methods

You can use REST APIs or file URLs to preview documents stored in TOS buckets. TOS lets you preview them as images, PDFs, or HTML.

tip

The processed results are returned immediately and are not saved in your bucket.

Using REST APIs

GET /example.docx?x-tos-process=doc-preview&x-tos-doc-src-type=docx&x-tos-doc-dst-type=jpg&x-tos-doc-page=1 HTTP/1.1
Host: endpoint
X-Tos-Content-Sha256: sha256
X-Tos-Date: 20220827T132948Z
Authorization: authorization

Using file URLs

http://bucket.endpoint/example.docx?x-tos-process=doc-preview&x-tos-doc-src-type=docx&x-tos-doc-dst-type=jpg&x-tos-doc-page=1

tip

To preview private files, use SDKs to generate pre-signed URLs that contain the document preview parameter.

Document preview features

Feature	Parameter	Description
Document preview	doc-preview	Displays documents stored in TOS buckets as images, PDFs, or HTML without opening them.

Last updated: 2026.08.20 17:53:16