Previews let people inspect files in the Files.com web interface without opening an external application. Supported files include images, audio, and video, PDFs, business documents, and text documents. The file's format, the chosen document editor, and the user's access determine which preview is available.

Preview-only access hides the normal Download action but still sends content to the browser. Use it to offer browser review, with the limits below in mind. Preview URLs have a limited validity period; reopen the preview if its URL has expired.

Required Permissions for Previewing

To open a preview in the web interface, a user needs List/Preview permission or Read permission or higher. List or Write permission alone does not allow previews. Folder permissions determine the account user's access; Share Link allowed actions govern visitors separately.

List/Preview Permission

Users with List/Preview permission can browse folders, see filenames, and open supported previews. They can preview images, audio, video, PDFs, the supported business document formats, and all supported text formats, including site-configured custom text extensions.

List/Preview permission does not allow the normal download action, uploads, modification, deletion, or sharing. A file that has no supported preview still appears in the listing but cannot be opened or downloaded. Users with Read permission or higher can also download files, including formats that cannot be previewed.

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

List/Preview Permission Is Not a Security Boundary

A preview transfers content to the browser. It does not guarantee that the browser receives only a derived preview asset. Without an automatic watermark, a PDF preview sends the original PDF byte-for-byte, including metadata and non-rendered content. A watermarked PDF preview sends a modified PDF copy.

Preview-only access does not prevent screenshots, screen recording, printing, copying text, browser extensions, developer tools, cached preview assets, or photographing the screen. It is not a substitute for Digital Rights Management (DRM), Data Loss Prevention (DLP), or Information Rights Management (IRM).

Watermarks can identify the recipient in image and PDF previews and discourage redistribution. The stored original remains unchanged, and normal downloads do not include the automatic watermark. Do not rely on watermarking to remove metadata or hidden content.

Thumbnails

Thumbnails represent files in Thumbnail and Grid views and in the Metadata panel. They appear for image, PDF, and document files in the web interface and the Desktop App's mounted drive. In the web interface, users need List/Preview or Read permission or higher to see them.

Displaying Thumbnail or Grid views does not record file activity or trigger notifications, Automations, or Webhooks. Explicitly opening a preview follows the activity rules below. Remote storage can still record the transfer used to generate a thumbnail.

File History and Notifications

Explicitly opening a file in the preview viewer records a Read event in file history and triggers matching Notifications and Webhooks. This applies to account users and Share Link visitors for every previewable file type.

Preview events and downloads use the same Read event type; history does not distinguish them. Business document previews open through the online editor and appear with the interface shown as "Office". Online editing activity explains the editor's download and conversion records.

Passively viewing a file listing's thumbnails does not create those records or trigger those messages.

Files on Remote Server Mounts

Files.com must retrieve file contents to generate previews for a Remote Server Mount. It caches preview data to avoid repeated transfers when the file has not changed.

The remote server may record thumbnail retrieval as a download even when Files.com does not record a Read event for the passive listing. That remote server cannot distinguish a transfer for thumbnail generation from one that opens a preview.

If the remote server automatically deletes files after download, thumbnail generation can therefore remove a source file. Use a Sync to create an independent copy in a folder that is not mounted when that behavior would disrupt the source workflow.

A Share Link that allows downloads also lets visitors preview supported files. A preview-only Share Link hides the normal Download action while still transferring preview content to the browser. Visitor permissions explain the available actions and supported preview types.

The listing defaults to Grid mode when most visible files are previewable. If fewer than half are previewable, it defaults to List mode. Visitors can switch between List, Thumbnail, and Grid mode.

Previewing Files