Documentation

Previewing Files

The Files.com web interface supports previewing a wide array of files, including images, business documents, text documents, and audio and video files. This lets users verify a file's contents without downloading it and opening it in an external program.

Previewing some types of files is supported for visitors to Share Links. Any Share Link that allows visitors to download also includes the option for visitors to preview supported file types. You can restrict the allowed actions for a Share Link so visitors can only preview files within the link without downloading them.

Required Permissions for Previewing

To render file previews within the Files.com web interface, the file contents are transferred to the user's browser and then rendered as a preview by that browser. The minimum permission required to preview files is List/Preview. Users with the Read permission or higher can also preview files. Users with only the List or Write permission cannot preview files.

List/Preview Permission

Users with the List/Preview permission can browse folders, see file names, and open previews for images, PDFs, business documents, audio, and video files. They cannot download the original file, upload, modify, delete, or share files. For these previewable file types, users see the rendered preview but the original file download is blocked. For all other file types, the file appears in the folder listing but cannot be previewed, opened or downloaded.

Users with the Read permission or higher can both preview and download files, including file types that are not previewable.

The List/Preview permission controls preview access through the Files.com Web App only. The Desktop App, Mobile App, FTP, SFTP, WebDAV, and the CLI do not offer preview-only access. Those clients and protocols follow standard read permission behavior.

List/Preview Permission Is Not a Security Boundary

The List/Preview permission blocks normal file download and allows users to preview images, PDFs, business documents, audio, and video files in the web browser. It does not prevent content exfiltration through screenshots, screen recording, printing, copy/paste from previews, browser extensions or apps that capture or save rendered page content, browser developer tools, cached preview assets, or photographing the screen. It is not a substitute for DRM, data loss prevention (DLP), or information rights management (IRM) solutions.

If your use case involves image or PDF files, consider adding Watermarks to overlay identifying information on previews, which can discourage casual redistribution.

Thumbnails

Thumbnails are small preview images that represent files. These inline previews appear in Thumbnail and Grid views, and in the Metadata panel for image, PDF, and document files in the Files.com web interface and Desktop App mounted drive. Users must have at minimum the List/Preview or Read permission to see these inline previews.

Using the Thumbnail or Grid mode does not log any file transfers, and does not trigger any type of notifications or webhooks.

Files on Remote Server Mounts

To display inline previews for a folder on a Remote Server Mount, the Files.com platform must access the contents of the file. To save resources, Files.com caches preview data, which prevents extraneous transfers for repeated viewing of a file that has not changed.

Viewing an inline preview is not considered a download by your site, does not log a download action, and does not trigger notifications, automations, or webhooks. However, the remote server may record the activity as a download, and it cannot distinguish between a transfer for creating previews and a transfer that is fetching the file. If the remote server automatically deletes files as soon as they are downloaded, consider using a Sync to copy the files to a folder that is not mounted, so previewing files does not trigger an auto-deletion on the source system.

File History and Notifications

Previewing an image, PDF, or audio or video file does not log a download action in the file history. The transfer of a file for previewing does not trigger notifications or webhooks.

Previewing text documents (source code, structured data, markdown, or text) is logged in the file history and triggers notifications and webhooks.

Previewing standard productivity suite format files transfers the file from your storage to the editor for previewing. This activity appears in your history with the interface "office." The transfer is logged and triggers notifications and webhooks.

Visitors to a Share Link that allows downloading see an interface similar to the Files.com web interface file listing, including inline image and PDF previews.

When the default view contains mostly previewable files, the view mode defaults to Grid mode. If fewer than half of the items the visitor sees when they open the link are previewable, the listing defaults to List mode. Visitors can switch at any time between List, Thumbnail, and Grid mode for the listing.